Driven by the phenomenal success of the Ultimate Fighting Championships (UFC) bouts on pay-per-view television, Mixed Martial Arts (MMA) is now the fastest-growing sport in the United States. As its name suggests, MMA combines techniques of various other fighting systems, including boxing, jujitsu, wrestling, judo, karate, kickboxing, kung fu, and taekwondo.

Decades after a Brazilian fighting style known as vale tudo (anything goes) began to spark local and international interest in the late 1920s, MMA burst into full-colour in America in 1993, with the formation of the UFC. Financed by the Semaphore Entertainment Group, led by New York music promoter Robert Meyrowitz, UFC bouts began more as violent spectacles than sporting events, with fighters from various disciplines battling it out in the same ring to the delight of bloodthirsty crowds.

Rorion Gracie, a Brazilian living in California, organized the first fight and designed the trademark arena, the Octagon. Aside from three simple rules of no biting, eye-gouging, or fish-hooking (placing your finger in an opponent's mouth and pulling backwards) the UFC prided itself on no-holds-barred fighting, with little regulation. Even as MMA's popularity grew, politicians condemned the sport, including John McCain, who in 1996 called it human cockfighting.

In November 2000, the UFC added weight classes and 28 more rules, outlawing head butts, hair pulling, and groin shots. As of May 2007, 23 states and the District of Columbia sanction MMA fights. Bouts consist of three five-minute rounds (five in title fights), and elbows, fists, choke holds, and armbars are allowed. Prominent MMA contenders include former wrestlers and professional boxers, as well as black belts in martial arts; most have trained in various disciplines.

When an MMA fighter is downed, he often lunges for his opponent's legs, hoping to take him down as well. Another common strategy is the ground and pound, where a fighter seeks to take down his opponent and stay on top while striking him with his fists and elbows at close range; this is often countered with the sprawl and brawl, where the opponent escapes the takedown by keeping his legs spread wide, out of reach, putting his weight on the other fighter and throwing punches from that angle.

The popularity of MMA among 18 to 34-year-old males, a demographic coveted by advertisers, is overwhelming: according to Sports Illustrated, the UFC scored pay-per-view revenues of US$223 million in 2006, compared to US$177 million for boxing and US$200 million for WWE (World Wrestling Entertainment). Various smaller leagues such as the World Combat League and the International Fight League also draw audiences. A UFC reality show, The Ultimate Fighter, began airing in 2005.