In this study peripheral blood erythropoietic parameters in 9 to 12-day-old neonatal rats suckled by experimentally-induced anemic mothers were examined. Stimulation of erythropoiesis in these pups was judged by increases in hematocrit, hemoglobin, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration. Failure to observe increases in reticulocytes may be, in part, the result of decreased maturation time, as indicated by reticulocyte Heilmeyer maturation indices in peripheral blood. The reticulocyte maturation curve was shifted to the left in neonates nursing from anemic mothers. These results suggest that erythropoietin (Ep) is transmitted to suckling rats via maternal milk, and by escaping inactivation in their gastrointestinal tract stimulates their erythropoiesis. These findings, in agreement with our previous work, are supportive of studies by others and further indicate a maternal-neonatal erythropoietic relation in rats.