Though rules have been adopted, there is no general sanctioning body for the sport, and the sets of rules vary according to the laws of individual organizations and localities. It was thought that Olympic recognition would be forthcoming for the 2004 Summer Olympics, held in Athens, under the banner of pankration. However, the International Olympic Committee was unconvinced that Greece could handle the total number of sports proposed. To placate the IOC, the organizers removed all new medal sports and pankration was excluded.

The techniques utilized in mixed martial arts competition generally fall into two categories: striking techniques (such as kicks, knees and punches) and grappling techniques (such as clinch holds, pinning holds, submission holds, sweeps, takedowns and throws). Some unarmed hand to hand combat techniques are considered illegal in most or all modern competition, such as biting, eye-gouging, fish-hooking and small joint manipulation. Over the last ten years, strikes to the groin have become illegal in all sanctioned organizations. The legality of other techniques such as elbows, headbutts and spinal locks vary according to competition or organization.

A victory in a bout is normally gained by the judges’ decision after an allotted amount of time has elapsed, a stoppage by the referee or the fight doctor (in the event that the competitor is injured or can no longer defend himself intelligently), a submission, by a competitor’s cornerman throwing in the towel, or by knockout.

While competition in the sport is occasionally depicted as brutal by the media, there was no death or crippling injury in a sanctioned event in North America until the death of Houston, Texas fighter Sam Vasquez on November 30, 2007. Vasquez collapsed shortly after being knocked out in the third round of an October 20 fight at the Toyota Center in Houston by Vince Libardi. Vasquez had two separate surgeries to remove blood clots from his brain, and shortly after the second operation suffered a major stroke and never regained consciousness. While questions have been asked about the Vasquez’s health before his final bout no firm indications of pre-existing problems has yet surfaced. Since he was age 35, he would have had to undergo extensive pre-fight medical screening in order to obtain a license to compete in Texas. The only other verified fatality in MMA competition is the 1998 death of Douglas Dedge in an unsanctioned fight in Ukraine. There are unconfirmed reports that Dedge had a pre-existing medical condition. A study by Johns Hopkins University concluded “The overall injury rate [excluding injury to the brain] in MMA competitions is now similar to other combat sports [involving striking], including boxing. Knockout rates are lower in MMA competitions than in boxing. This suggests a reduced risk of TBI in MMA competitions when compared to other events involving striking.”

One of the earliest forms of widespread unarmed combat sports with minimal rules was Greek pankration, which was introduced into the Olympic Games in 648 B.C. Even as late as the Early Middle Ages, statues were put up in Rome and other cities to honour remarkable pankratiasts.

No-holds-barred events reportedly took place in the late 1800s when wrestlers representing a huge range of fighting styles including various catch wrestling styles, Greco-Roman wrestling and many others met in tournaments and music-hall challenge matches throughout Europe. The first major encounter between a boxer and a wrestler in modern times took place in 1887 when John L. Sullivan, then heavyweight world boxing champion, entered the ring with his trainer, Greco-Roman wrestling champion William Muldoon, and was slammed to the mat in two minutes. The next publicized encounter occurred in the late 1890s when future heavyweight boxing champion Bob Fitzsimmons took on European Greco-Roman wrestling champion Ernest Roeber. Reportedly, Roeber suffered a fractured cheekbone in this bout, but was able to get Fitzsimmons down on the mat, where he applied an armlock and made the boxer submit. In 1936, heavyweight boxing contender Kingfish Levinsky and veteran professional wrestler Ray Steele competed in a mixed match, which Steele won in 35 seconds.

Another early example of mixed martial arts combat was the martial art of Bartitsu, founded in London in 1899, which was the first martial art known to have combined Asian and European fighting styles, and which saw MMA-style contests throughout England, pitting European and Japanese champions against representatives of various European wrestling styles.

Mixed style contests such as boxing vs. jujutsu were popular entertainment throughout Europe, Japan and the Pacific Rim during the early 1900s. In Japan these contests were known as Merikan, from the Japanese slang for “American [fighting]”. Merikan contests were fought under a variety of rules including points decision, best of three throws or knockdowns, and victory via knockout or submission.

Professional wrestling died out after World War I and was reborn in two streams: “shoot”, in which the fighters actually competed, and “show,” which evolved into modern sports entertainment professional wrestling.

Modern mixed martial arts tournaments are rooted in two interconnected movements. First were the vale tudo events in Brazil, followed by the Japanese shoot wrestling shows. Vale tudo began in the 1920s with the “Gracie challenge” issued by Carlos Gracie and Hélio Gracie and upheld later on by descendants of the Gracie family. In Japan in the 1970s, a series of mixed martial arts matches were hosted by Antonio Inoki, inspiring the shoot-style movement in Japanese professional wrestling, which eventually led to the formation of the first mixed martial arts organizations, such as Shooto, which was formed in 1985. The concept of combining the elements of multiple martial arts was pioneered and popularized by Bruce Lee in the late 1960’s to early 1970’s. Lee believed that “the best fighter is not a Boxer, Karate or Judo man. The best fighter is someone who can adapt to any style.” His innovative concepts were recognized in 2004 by UFC President Dana White when he called Lee the “father of mixed martial arts.”

Mixed martial arts gained significant international exposure and widespread publicity in the United States in 1993, when Royce Gracie won the first Ultimate Fighting Championship, sparking a revolution in the martial arts. In Japan in 1997, the continued interest in the sport eventually resulted in the creation of the PRIDE Fighting Championships.
Chuck Liddell (right) and Tito Ortiz broke PPV records with their rematch at UFC 66.

The United States Army began to sanction Mixed Martial arts when the US Army Combatives School held the first annual All Army Combatives Championships in Nov 2005.

The sport reached a new peak of popularity in North America in the December 2006 rematch between then light-heavyweight champion Chuck Liddell and former champion Tito Ortiz, rivaling the PPV sales of some of the biggest boxing events of all time, and helping the UFC’s 2006 PPV gross surpass that of any promotion in PPV history. In 2007, Zuffa LLC, the owners of the UFC MMA production, bought Japanese rival MMA brand PRIDE merging the contracted fighters. and drawing comparisons to the consolidation that occurred in other sports, such as the AFL-NFL Merger in American football.

As a result of sporting events, martial arts training, information sharing, and modern kinesiology, the understanding of the combat-effectiveness of various strategies has been greatly improved. UFC commentator Joe Rogan has claimed that martial arts have evolved more in the ten years following 1993 than in the preceding 700 years.

The early years of the sport saw a wide variety of traditional styles—everything from sumo to kickboxing— and the continual evolution of the sport has gradually eliminated less effective techniques and “pure” styles, usually because specialized fighters were lacking in skills to deal with broader techniques.

In the early 1990s, three styles stood out for their effectiveness in competition: Brazilian Jiu-Jitsu, amateur wrestling and shoot wrestling. This may be attributable in part to the grappling emphasis of the aforementioned styles, which, perhaps due to the scarcity of mixed martial arts competitions prior to the early 90s, had been neglected by most practitioners of striking-based arts.

Fighters who combined amateur wrestling with striking techniques dominated the standing portion of a fight, whilst Brazilian Jiu-Jitsu stylists had a distinct advantage on the ground: those unfamiliar with submission grappling proved to be unprepared to deal with its submission techniques. Shoot wrestling practitioners offered a balance of amateur wrestling ability and catch wrestling based submissions, resulting in a generally well-rounded set of skills. The shoot wrestlers were especially successful in Japan, where this style initially dominated others.

As competitions became more and more common, those with a base in striking became more competitive as they acquainted themselves with takedowns and submission holds, leading to notable upsets against the then dominant grapplers. Subsequently, those from the varying grappling styles learned from each other’s strengths and shortcomings, and added striking techniques to their arsenal. This overall development of increased cross-training resulted in the fighters becoming increasingly multi-dimensional and well-rounded in their skills. One of the first fighters to be considered the prototype for mixed martial arts was UFC middleweight champion, Frank Shamrock. “During his reign atop the sport in the late 1990s he was the prototype — he could strike with the best strikers; he could grapple with the best grapplers; his endurance was second to none.”

Today, mixed martial artists train in a variety of styles that have been proven effective in the ring, so that they can be effective in all the phases of combat. Although fighters will try to play to their particular specialties, they will inevitably encounter all kinds of situations; a stand-up fighting specialist will probably get taken down at some point and a submission artist might need to fight standing-up for a while before he can execute a takedown. A mixed martial artist might train in a particular style to enhance his or her skills in the phase of combat that that style targets. Typical styles, known for their effectiveness, that have been trained prior to the mixed martial arts career, and that are trained individually to enhance a particular phase of combat, are:
Stand-up: Various forms of Boxing, kickboxing, Muay Thai, and/or forms of full contact karate are trained to improve footwork, elbowing, kicking, kneeing and punching.
Clinch: Freestyle and Greco-Roman wrestling, Sambo, and Judo are trained to improve clinching, takedowns and throws, while Muay Thai is trained to improve the striking aspect of the clinch.
Ground: Brazilian Jiu-Jitsu, shoot wrestling, catch wrestling, Judo, and Sambo are trained to improve submission holds, and defense against them. These styles are also trained to improve and maintain ground control.

Many styles have to be adapted slightly for use in the sport. For example, several boxing stances are ineffective because they leave fighters vulnerable to leg kicks or takedowns. Similarly, Judo techniques have to be adapted to an opponent not wearing a judogi. Usually, modern fighters do not train in any particular style, but either train in multiple styles with multiple coaches, or train in teams with other athletes focusing specifically on competition. Energy system training, speed drills, strength training and flexibility are also important aspects of an MMA fighter’s training. Mixed martial arts competition is very demanding physically, and the athletes need to be in top condition to be successful.

While mixed martial arts was initially practiced almost exclusively by competitive fighters, this is no longer the case. As the sport has become more mainstream and more widely taught, it has become accessible to wider range of practitioners of all ages. Proponents of this sort of training argue that it is safe for anyone, of any age, with varying levels of competitiveness

The following are various nicknames applied to different fighting styles. Apart from the fact that fighters are usually much more versed in one particular fighting style such as Brazilian Jiu-Jitsu, judo, Muay Thai, wrestling, or other martial art, the following terms are used to describe how a particular fighter is attempting to accomplish a particular victory. For instance, BJ Penn and Fedor Emelianenko score victories by striking, “ground and pounding,” and submitting, depending on the strengths of their opponents. Note that some of these are not complete styles; rather, they are merely phases in a fighter’s game.

Sprawl-and-brawl is a stand-up fighting tactic that consists of effective stand-up striking, while avoiding ground fighting, typically by using sprawls to defend against takedowns.

A sprawl-and-brawler is usually a boxer, kickboxer, Thai boxer and/or full contact karate fighter who has trained in wrestling to avoid takedowns and tries to keep the fight standing. Usually these fighters will study enough submission wrestling so that in the unfortunate event that they are taken down to the ground, they can tie their opponents up and survive long enough to either get back to standing or until the referee restarts the fight. This style is deceptively different from regular kickboxing styles, since sprawl-and-brawlers must adapt their techniques to incorporate takedown and ground fighting defense. Two of the most successful sprawl-and-brawlers are Chuck Liddell and Mirko Filipović.

Clinch fighting and “Dirty boxing” are tactics consisting of using a clinch hold to prevent the opponent from moving away into more distant striking range, while at the same time attempting takedowns and striking the opponent using knees, stomps, elbows, and punches.

The clinch is usually utilized by wrestlers that have added in components of the striking game (typically boxing), and Muay Thai fighters. Often, wrestlers that have added the striking game are partial to strikes from within the clinch, particularly wrestlers who have already developed a strong clinch game. In the case that an exchange on the feet does not go in their favor, they can bring the fight to the ground quickly as their true expertise lies in wrestling, so they are ultimately less timid about trading blows. Through the use of Greco-Roman clinching techniques and Muay Thai strikes, neck clinching and body locks clinch fighting could be used to devastate ill-prepared opponents.

Wrestling components include pummelling and underhooking arms along with “bodylocking” the waist. Pummelling is commonly learned as a drill and is similar to Muay Thai’s “snaking hands” drill used for practicing the neck or “plumb” clinch. With neck pummelling (plumb), the back of the head - not the neck - is used for greater leverage.

Muay Thai typically employs the plumb clinch where the back of the head is held. From here one can knee, wrestle, stomp the feet and calf, or perform sweeps using the feet and knees as leverage, much like trips and slams in freestyle wrestling. Thai boxers will also clinch or bodylock the waist and either perform throws or force the opponent to the floor using their chin into the opponents chest as the force and the bodylock as the fulcrum, with the legs providing thrust. Randy Couture and Wanderlei Silva are examples of effective clinch fighters.

Ground-and-pound is a ground fighting tactic consisting of taking an opponent to the ground using a takedown or throw, obtaining a top position, and then striking the opponent. Ground-and-pound is also used as a precursor to attempting submission holds.

This style is used by wrestlers or other fighters well-versed in defending submission holds and skilled at takedowns. They take the fight to the ground, maintain a grappling position, and strike until their opponent submits, is knocked out or is cut so badly that the fight cannot continue. Although not traditionally considered a conventional method of striking, the effectiveness and reliability (as well as recently-developing science) of this style is proven. Originally, most fighters who relied on striking on the ground were wrestlers, but considering how many fights end up on the ground and how increasingly competitive today’s MMA is, strikes on the ground are becoming more essential to a fighter’s training. Ground-and-pound was first displayed as an effective technique by UFC and PRIDE champion, Mark Coleman. Other examples of ground-and-pound fighters are Fedor Emelianenko and Tito Ortiz.