Hematologic abnormalities in childhood Pb poisoning may be partially due to the presence of other disorders, such as Fe deficiency or thalassemia minor. Increased Pb burden as a cause of microcytic anemia was reassessed by studying 58 children with class III or IV Pb poisoning, normal Fe stores and no inherited hemoglobinopathy. Anemia occurred in 12% and microcytosis in 21% of these children. The combination of anemia and microcytosis was found in only 1 of 58 patients (2%). When only children with class IV Pb poisoning were studied, the occurrence of microcytosis increased to 46%. However, the combination of microcytosis and anemia was found in only 1 of these 13 more severely affected patients. Microcytic anemia was similarly uncommon in children with either blood Pb concentration .gtoreq. 50 .mu.g/100 ml or erythrocyte protoporphyrin concentration .gtoreq. 110 .mu.g/100 ml. Microcytosis and anemia evidently occur much less commonly than previously reported in childhood Pb poisoning uncomplicated by other hematologic disorders.