The First National Environmental Health Survey of Child Care Centers was conducted to provide information about lead, allergen, and pesticide levels in licensed U.S. child care centers. Lead levels were measured in settled dust, paint, and play area soil; indoor allergen levels were measured in settled dust; and pesticide residues were measured on indoor surfaces and in play area soil. Fourteen percent of centers had significant lead hazards, suggesting that an estimated 470,000 children under age six (approximately 10% of all children in licensed centers) attend centers with significant lead hazards. Approximately 5% of centers had levels of allergens associated with asthma and allergic conditions. Three-quarters of centers had pesticides applied (either indoors or outdoors) during the previous year. Although most centers did not appear to present risks from lead and allergens, some centers did have unsafe levels of these contaminants. These conclusions cannot be generalized to unlicensed child care arrangements. (author abstract)