Twenty-two female monkeys (Macaca irus) were given lead acetate by an intramuscular route during pregnancy and/or lactation. A high dose of lead (5 mg Pb2+/kg/day) can induce abortions and death in pregnant monkeys. At a lower dose (1 mg Pb2+/kg/day), the foetus can be exposed to lead via placenta and/or maternal milk. Studies using optical microscopy showed the typical renal lesions in mothers treated during pregnancy (five months) and an erythrodiapedesis in cerebral matter of the new-born at birth.