[C-14]-Ametryn was administered to rats, lactating goats, and laying hens. Excreta from all three species, daily milk from the goats, and egg samples from the hens were collected. In addition, selected tissues were taken following animal sacrifice. All samples were analyzed to determine the total radioactive residues, and metabolites were identified and quantified in excreta and selected tissues. The results showed that, in all three species, the majority of the administered dose was eliminated in excreta. Residues were observed in milk, eggs, tissues, and organs; liver and kidney showed the highest total radioactive residue levels. Metabolites in the rat were isolated, purified, and identified by thin-layer chromatography, high performance liquid chromatography, and various mass spectroscopic techniques. Ametryn appears to undergo extensive metabolic transformation by N-dealkylation, oxidation/hydroxylation, and conjugation (with sulfate, glutathione derivatives, and glucuronic acid). The results obtained from the rat were compared with those obtained from the ruminants and poultry.