The hepatotoxic effect of aflatoxin B1 on pregnant rats was studied by injecting the animals in the first 14 days of pregnancy with doses equivalent ot 1/1,000 ppm; the rats were killed at the end of pregnancy. Liver lesions such as clear intumescence, granular dystrophy, Kupffer cell hyperplasia, pycnosis and atypical mitoses were shown; concomitantly regeneration phenomena were expressed by an increased incidence of binucleated cells and mitosis. Fertility decreased after aflatoxin and embryonary resorptions, malformations and developmental retardations occurred.