Data on bicycle injury presentations at a public hospital emergency department for 1991-95 inclusive were analysed to determine the nature and extent of bicycle injuries in the community. There were 599 bicycle injury presentations during the study period, representing more than 2.0% of all injury-related presentations to the emergency department. The main outcome measures were severity and type of injury. Distribution by gender, age, helmet use (1991 and 1992 only), location and mechanism was examined. Rider-only injuries (falls or collisions with stationary objects) accounted for 79.3% of all presentations with only 5.2% due to collisions on a public road or footpath with other moving traffic. Of all injuries where a location was determined, 61.6% occurred in off-road locations. There was little difference in the overall proportions of hospital admissions from injuries on-road (12.4%) and off-road (9.0%). Cyclists injured in on-road collisions with traffic had a higher proportion of hospital admissions (40.0%) than those injured on-road by other mechanisms (7.6%). Children under 10 years of age who had been riding without a helmet suffered a much higher proportion of injuries to the head (53.2% of all injuries) than older cyclists riding without a helmet (19.4%). The majority (83.1%) of head injuries in children under 10 years of age occurred off-road and helmet use was lowest in this group (28.6%). Given previous evidence that helmet use can prevent head injuries, strategies to increase helmet use among cyclists, particularly young children, while riding both on and off-road, should be given a high priority. Rider-only injuries are also an important public health issue.