Two hundred sixty-five members of 21 off-road cycling clubs in 12 states completed a four-page questionnaire regarding their riding habits and injury history for the 1992 cycling season. The response rate was 62.4%. Of those surveyed, 85.7% reported injuries that were sustained while mountain biking during the preceding 12 months, with abrasions, contusions, and lacerations being reported most frequently. Injuries were considered significant if the cyclist sought medical attention for the injury and was unable to ride for at least 1 day due to the injury. Sixty injuries met these criteria. Of those, 90% were traumatic in nature, making the incidence of significant traumatic injury 20.4% in this group for the year studied. Fractures were the most common significant traumatic injury reported. The shoulder complex was the most commonly injured anatomic region. Loss of control, high-speed descent, and competitive activity level were identified as variables associated with traumatic injury. Competitive activity level was the only independent risk factor positively associated with traumatic injury, with an adjusted odds ratio of 4.24 (p < 0.0001).