OBJECTIVES: To examine resource use and cost of Emergency Department (ED) and hospital care for acute injuries resulting from motorcycle accidents. METHODS: 2003 ED visit and hospital discharge data from Massachusetts, where a mandatory all age helmet law applies, were analyzed. Cases with motorcycle accident-related injuries were identified by ICD-9 diagnosis and external cause codes (E codes: E810.2-E825.2, E810.3-E825.3). Inpatient cases were restricted to those admitted via ED. Type and circumstance of injury, time of occurrence, demographics, costs, length of stay (LOS)/visit, and disposition were examined. Charges were adjusted by a 0.55 cost-to-charge ratio and adjusted to national values. Cost estimates (2003US$) include accommodations and ancillary services. RESULTS: Acute injuries from motorcycle accidents resulted in 3,066 ED visits and 420 hospitalizations during the year. Males comprised 87% of cases; injured party was driver in 95%. Mean age was 32 years (49% < 30 years). The majority (76%) occurred between May-September, Friday-Sunday (52%), and 4:00 PM-midnight (54%). Multiple injuries were noted in 44% of cases. Head injury/skull fractures were coded for 8%. Fatalities were noted in <1% of cases. On average, hospital LOS was 7 days (±10.1) with cost per stay of $19,535 (±$34,688). At hospital discharge, 82% went home (14% with home care), 17% transferred to sub-acute facilities, 1% AMA. ED visit cost without hospitalization was $787 (±$1,136) and was 2.7 hours (±3), on average. Management of these injuries resulted in use of 2,877 hospital days and 9,274 ED visit hours at a cumulative cost of $10.5 million. CONCLUSIONS: This analysis shows that nearly half of the motorcycle accident victims sustained more than one injury; the majority survived, and most acute injuries were managed successfully in the ED. Although substantial, these acute care costs are conservative estimates of injury-related costs, as they do not include physician-related or post-acute care costs.