Although the mechanical bull was originally designed to train cowboys for the rodeo, nearly 1,000 of these machines are in use in night clubs and amusement parks throughout the United States. We have treated 84 mechanical-bull-related injuries in our institution, the most common to the groin and the lower extremity (32%). A common fracture, which we have labeled the bullrider's thumb, involved the proximal phalanx of the thumb and occurred as the patient's body forced his thumb against the horn of the machine. We describe the mechanical bull, its mechanism of action, and the injuries possible while riding or falling from the bull.