Aflatoxin B1 is a highly toxic fungal metabolite frequently found in animal feeds and human foodstuffs contaminated by mold Aspergillus. It is the most potent hepatocarcinogen known for rats. The objectives of the proposed investigation is to determine the metabolic fate of aflatoxin B1 in Rhesus monkeys under conditions which simulate actual human exposures to aflatoxins, and to provide comparative animal data which can then be used to estimate human responsiveness. The research is also aimed at isolation, identification and quantitative determination of the major urinary metabolites of aflatoxin B1. The kinetics of metabolism of aflatoxin B1 by the microsomal enzymes of monkey and human livers will be compared to facilitate the interpretation of the human toxicity from animal data. Highly radioactive, pure, aflatoxin B1 will be prepared and administered orally at subtoxic levels to young Rhesus monkeys under protein-deficient dietary conditions. The radioactive aflatoxin B1 and its metabolites will be quantitatively traced, and the major metabolites, including aflatoxin P1 and aflatoxin M1, will be identified and measured. The toxicity of the metabolites will be tested on one- day-old ducklings, chick embryos, and cell cultures, to identify the active form of the toxic agent. A detection method for aflatoxin exposure by determination of aflatoxin P1 in the urine samples will be developed.