Mild leukopenia and thrombocytopenia are common in multitransfused hemophiliacs. Because little attention has previously been directed to measurements of erythropoiesis in these patients, we prospectively examined hemoglobin concentration and RBC indices in 94 children and young adults with hemophilia during comprehensive clinic visits. Additional studies performed in many included serum transferrin saturation, ferritin, haptoglobin, and free erythrocyte protoporphyrin measurements. Hemoglobin concentrations were recorded as age-related percentile values. Hemophiliacs of all ages and degrees of severity often had lower than average values for hemoglobin; 31% had values less than the third percentile, 46% less than the tenth percentile, and 83% less than the mean value. Reduced hemoglobin percentile values were unrelated to age, severity of disease, or human immunodeficiency virus antibody status. Only five patients had an obvious cause for anemia. Serum ferritin, transferrin saturation, and erythrocyte protoporphyrin values were usually normal, indicating that iron deficiency and anemia of chronic disease were uncommon. Although serum haptoglobin was reduced in 44% of the patients, reticulocyte count was infrequently increased. We conclude that hemoglobin values are frequently less than the mean normal values for age in hemophiliacs. Although frank anemia is common, it is usually mild and without obvious cause. Hemophiliac individuals with slightly reduced hemoglobin values probably do not routinely require detailed investigation for occult blood loss, iron deficiency, or inflammation.