Lead toxicity has been studied in the juvenile baboon using both daily intravenous injections of lead chloride and ingestion of leaded paint and lead paint pigments. Approximate steady state blood lead concentrations of 0.9 and 0.08 mg% were obtained after one week of intravenous injections of either 5.0 and 0.5 mg of lead per day, respectively. The onset of clinical symptomatology was noted after only one week of 5.0 mg/day injections culminating in convulsions and blindness after 40 days. The interrelationship of variations in the blood lead concentration, the clinical symptomatology of toxicity and the biochemistry of heme formation, have been explored in response to controlled exposures to lead.