An animal model for asymptomatic and overt lead toxicity is presented in which rabbit pups, 1 to 30 days of age, were fed a milk supplement containing Pb(NO3)2. Reduced body growth, increased mortality, hematologic abnormalities, kidney and liver histopathology, as well as encephalopathy, were observed in rabbits 2 to 30 days of age ingesting more than 2.8 mg of Pb/day. At the highest dose, brain lesions were widespread, involving the frontal and occipital cortex, striatum, hippocampus, and cerebellum. At moderate doses, the region most affected was the cerebellum. At the lowest dose no alteration in body, brain growth, mortality, or tissue histology was evident; however, basophilic stippling was observed. As a group, these asymptomatic rabbits generally exhibited higher activity than non-lead-fed littermates. The rabbit model presented here should provide many advantages in the study of lead toxicity on the developing nervous system, since (a) maximum brain development in the rabbit, like that in rhesus monkey and man, occurs perinatally, and (b) the effects of lead toxicity in the rabbit closely parallel those in man.