Objective: To compare rates, circumstances, and outcomes of cyclist crashes between children (aged 0-9 years), adolescents (aged 10-19 years), and adults (aged 20 years and over) in Victoria, Australia. Methods: A retrospective analysis of cyclist crashes in police records and the Victorian Admitted Episodes Dataset during the period 2004-2008. Results: Adolescent cyclists had the highest rates, per 100 000 people, of police-reported (32.6, 95% confidence interval [CI]: 30.7-34.5) and hospitalized cyclist crashes (71.6, 95% CI: 68.7-74.4). Police-reported helmet use at the time of the crash was lowest among children (57.1%, 95% CI: 49.5-64.8) compared to 60.2 percent (95% CI: 57.3-63.1) in adolescents and 77.7 percent (95% CI: 76.5-78.8) in adults. This was reflected in the hospital data, which indicated that more than one third of cyclist hospitalizations among children (37.4%) resulted in head injuries compared to around 1 in 4 hospitalized cyclist crashes in adolescents (26.8%) and adults (23.7%). Cyclists emerging off a footpath into the path of a vehicle as well as cyclists struck by vehicles emerging form a driveway were the most frequent types of police-reported crashes involving children (73.9%) and adolescents (48.1%). In contrast, most adult cyclist crashes occurred on the roadway, mainly at intersections. Conclusions: Programs to improve the safety knowledge and behavior of children and adolescent cyclists, particularly focusing on helmet use, should be part of a comprehensive approach that encompasses legislative and environmental changes, including appropriate cyclist facilities and reduced speed limit in residential areas.