We evaluated the effectiveness of a community-based injury prevention program designed to reduce the incidence of burns, falls in the home, motor vehicle occupant injuries, and poisonings and suffocations among children ages 0-5 years. Between September 1980 and June 1982, we implemented five injury prevention projects concurrently in nine Massachusetts cities and town; five sites, matched on selected demographic characteristics, were control communities. An estimated 42 percent of households with children ages 0-5 years were exposed to one or more of the interventions over the two-year period in the nine communities. Participation in safety programs increased three-fold in the intervention communities and two-fold in the control communities. Safety knowledge and practices increased in both intervention and control communities. Households that reported participatory exposure to the interventions had higher safety knowledge and behavior scores than those that received other community exposure or no exposure to intervention activities. We found a distinct reduction in motor vehicle occupant injuries among children ages 0-5 years in the intervention compared with control communities, associated with participatory exposure of about 55 percent of households with children ages 0-5 years. We have no evidence that the coordinated intervention programs reduced the other target injuries--although exposure to prevention messages was associated with safety behaviors for burns and poisonings.