Evaluations of the toxic and teratogenic effects of four aromatic amines, acridine, aniline, pyridine, and quinoline, have been made on amphibian (Xenopus laevis) embryos. For toxicity testing, the embryos were divided into three groups according to stage of development: Group I were mid-blastulae, Group II were tailbud embryos, and Group III were swimming larvae. Of the amines tested, acridine and quinoline were the most toxic, followed by aniline and pyridine. Ninety six hr LC50 values for acridine, quinoline, aniline, and pyridine were 4.5, 95, 150, and 1090 mg/L, respectively, for Group III larvae. Except for acridine, where embryos in all three groups were about equally affected, those in Group II were less sensitive to the other amines than those in Groups I and III. Group I embryos were exposed to all four amines to determine their teratogenicity. The amines were ranked in order to decreasing teratogenicity: acridine, quinoline, aniline, and pyridine having 96-hr EC50 values of 2.4, 29, 370, and 1200 mg/L, respectively. Electron microscopic examination of Group III larvae exposed to these amines reveals pathology of the spinal cord and musculature. This damage was correlated with immobility of the larvae. The uptake of acridine was followed in larvae (Group III) exposed to 5 mg/L and was found to reach a maximum level of about 85 mg/g wet weight in about one hr. Depuration kinetics were characterized by a rapid loss of 70% of the total acridine within 45 min. Acridine was undetectable after two hr. These data suggest that acridine, aniline, and quinoline have toxic and teratogenic effects at sufficiently low concentrations as to make them potential environmental hazards.