To better understand the epidemiology of accidents affecting wheelchair users, we evaluated 2,066 nonfatal wheelchair-related accidents reported, between 1986 and 1990, to the National Electronic Injury Surveillance System (NEISS) Division of the United States Consumer Product Safety Commission. The NEISS used data from representative emergency departments across the United States during this period. An extrapolation from this sample and from those of 1991 and 1992 provided an average national estimate of 36,559 wheelchair-related accidents per year that are serious enough to cause the injured person to seek attention at an emergency department; there was a significant (P = 0.007) upward trend over time. Elderly women were the most likely to sustain an injury. Of the people injured, 7.6% were not wheelchair users themselves. The most common causes of accidents were related to falls and tips in 73.2% of incidents, associated secondary causes (e.g., a ramp) in 41.4% and transfers in 16.9%. The most frequently reported location for the falls was at home (50.8%). The majority of resulting injuries were contusions and abrasions (32.8%), lacerations (28.0%), fractures (20.2%) and sprains and strains (10.3%). Hospitalization was required in 12% of cases. The results of this analysis have implications for rehabilitation professionals, regulatory bodies and wheelchair manufacturers.