An in vivo/in vitro toxicological screen (Tox Screen) has been developed to evaluate potentially hazardous waste samples and process stream residuals. The biological methods employed in the screen are designed to be rapid, inexpensive methods capable of screening large numbers of wastes. Emphasis is placed on identifying a wide range of potential toxic responses associated with each waste by employing diverse test methods. The toxic endpoints identified by the screen include mutagenesis/carcinogenesis, general toxicology, neurotoxicology, reproductive toxicology, teratology, and immunotoxicology. The protocol, called the Tox Screen, involves the oral administration of waste material to rodents for 10 consecutive days. At the end of the 10-day period the whole animal, body tissues and fluids are evaluated for toxicity. A major goal of the Tox Screen is to maximize the amount and type of potential health effects information that can be obtained by exposing metabolically competent intact animals to complex waste mixtures.