Bromochloroacetic acid is a water disinfection by-product. Bromochloroacetic acid was nominated for toxicity and carcinogenicity studies in rats and mice because of widespread human exposure and because a related dihaloacetate, dichloroacetate, was found to be carcinogenic to the liver of rats and mice. Drinking water was selected as the route of exposure to mimic human exposure to this chemical. Male and female F344/N rats and B6C3F1 mice were exposed to bromochloroacetic acid (greater than 95% pure) in drinking water for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in ¿Salmonella typhimurium,¿ ¿Escherichia coli,¿ and peripheral blood erythrocytes of exposed mice. Illustrations.