Preliminary evidence by Dr. J. Bus, in Biochemical Toxicology indicated that multiple oral dosing of 14C-Aniline HCI in adult male rats resulted in an increase in spleen weight and significant accumulation of radioactivity (aniline and/or metabolites) in the spleen. Long-term studies on aniline indicate splenic toxicity in male rats but not females. NCI Bioassay studies implicate aniline in the development of splenic angiosarcomas. Aniline was chosen for teratological examination based on these findings and human exposure data wherein aniline causes methemoglobinemia, anemia and nervous disorders. The hypothesis is that pregnant females and their young may be at especial risk to perturbations in the hematopoietic system since the fetal spleen is a major blood-forming organ and since the nervous system is vulnerable to even transient diminution in oxygen-carrying capacity. Thus the developing nervous system may be at special risk.