The incidence of twin births in the United States (US) has increased more than 65 per cent since 1980. However, the risk of injury to multiple-birth children is unknown. We sought to compare the risk of injury-related hospitalization and death between multiples and singletons. We conducted a retrospective cohort study using linked birth certificate, hospital discharge, and death certificate data from Washington State (1987-2002). All multiples and approximately three singletons randomly selected for each multiple pregnancy were included. We used Cox proportional hazards regression to determine the hazard ratio (HR) of injury-related hospitalization and death in the first six years of life for twins and triplets compared to singletons. The HRs of injury-related hospitalization were 1.4 for twins (95% confidence interval [CI]: 1.2-1.6) and 2.9 for triplets (95% CI: 0.5-9.5) relative to singletons after adjustment for child's sex, mother's age and marital status, and number of older siblings. Low birth weight significantly modified the association between twin status and injury hospitalization. The risk of injury death was not significantly higher among twins than singleton children. Twins appear to be at higher risk of childhood injury hospitalization. Triplets had a nearly three-fold increased rate of injury hospitalization compared to singletons, though we cannot exclude chance as an explanation. (Contains 4 tables.)