• Using data on all inpatients in 16 Michigan hospitals from 1980 through 1985, the clinical effects of a mandatory child restraint law were examined. Time-series analytic techniques revealed a 36% decline in hospitalization for all injuries, with a 25% decline for head injuries, and a 20% decline for extremity injuries for children younger than 4 years. In addition, length of stay declined for children hospitalized secondary to motor vehicle crashes. This study confirms the effectiveness of the child restraint law in Michigan, previously demonstrated by analyses of police records. Current hospital databases may be able to serve as one component for the implementation of comprehensive injury surveillance systems.