The contribution of residential hazards to children's health is poorly defined, but it is clear that some of the most prevalent disease and disabilities among U.S. children - including injuries and lead poisoning - would decline if such hazards were eliminated. Residential hazards also contribute to social disparities in children's health. This revised community-based participatory research application - a partnership of the Cincinnati Children's Hospital and the National tenter for Healthy Housing - would extend the follow-up of an ongoing 402-person birth cohort (n=358 in the randomized trial) designed to test the efficacy of interventions to control residential hazards in children, from 2 years of age through 5 years. This extension is critical to fully evaluate the efficacy of reducing lead and injury hazards on children's intellectual abilities, behavioral problems and injuries during the peak vulnerability of early childhood. The central hypothesis of this application is that housing interventions will reduce the prevalence of lead toxicity and residential injuries in a racially diverse sample of children. The aims and hypotheses of this application are: 1.0 Determine the efficacy of lead hazard controls on children's blood lead levels and their risk for learning and behavioral problems. 1.1 Levels of lead in dust, soil and water will be significantly lower for housing units in the lead treatment arm compared with the injury control arm at 36, 48 and 60 month home visits. 1.2 Children who are assigned to the lead treatment arm will have lifetime blood lead levels that are >20% lower than children assigned to the injury treatment arm at 5 years. 1.3 Children in the lead treatment arm will have higher IQ scores at 5 years than children in the injury treatment arm. 1.4 Children in the lead treatment arm will have fewer behavioral problems at 5 years, especially measures related to ADHD, than children in the injury treatment arm. 1.5 Higher lead exposure, measured during pregnancy and early childhood using maternal blood, cord blood, meconium and children's blood, is inversely associated with IQ scores and directly associated with behavioral problems at 5 years in children with postnatal maximal blood lead levels <5 /jg/dL 2.0 Determine the efficacy of comprehensive housing modifications on children's risk for injuries. 2.1 Children who are assigned to a multifactorial, housing intervention to prevent injuries will have 30% fewer unscheduled medical visits for housing injuries compared with children in the lead treatment arm. This is the first trial to test the efficacy of a multifactorial intervention for the primary prevention of two of the most prevalent causes of disease and disability in US children - lead toxicity and residential injuries. If efficacious, policy could be developed to reduce disease and disability linked with these hazards. It would also help resolve the ongoing controversy about the adverse consequences of low-level lead toxicity at blood lead levels previously thought to be safe. Our partnership with the National Center for Healthy Housing will enhance our ability to translate and disseminate the research results to affected communities locally and nationally.