Extreme sports (including in-line skating, snowboarding, mountain bicycling, extreme skiing, rock climbing, indoor tackle football, kickboxing, skateboarding, and ultra-endurance racing) are growing in popularity. Often these sports are designed to expose athletes to greater thrills and risks than are found in traditional sporting activities. Despite this increased risk of injury, athletes competing in these sports often have little or no formal medical coverage. This article reviews what is known about this emerging area of sports medicine to assist physicians in preparing for medical coverage of these athletes and their competitions.