• The signs and symptoms of methylmercury poisoning and the concentrations of mercury in samples of blood, hair, and milk are reported and compared in two infant-mother pairs exposed in the recent Iraq outbreak.1 In one pair, the infant was born prior to the exposure of the mother, and was exposed only from ingestion of methylmercury in mother's milk. In the other pair, the mother was exposed during pregnancy and did not breast feed the infant, who died 30 days after birth. Both mothers had some signs and symptoms of poisoning, but the infants did not. The infants had maximum estimated blood mercury levels between