Sodium nitrite administered in the drinking water to Long-Evans rats during pregnancy and lactation severely affected arythropoietic development, growth and mortality in their offspring. There were no significant differences between treated and control litters at birth. Thereafter, pups of treated dams on 2 and 3 q NaNO2/L gained less weight, progressively became severely anemic and began to die by the third week postpartum. By the second week postpartum, hemoglobin levels, RBC count, and MCV's of these pups were all drastically reduced compared to controls. Blood smears showed marked anisocytosis and hypochromasia. Gross chylous serum lipemia and fatty liver degeneration were noted. The data presented are consistent with the lactational induction of severe iron deficiency in the neonata.