Iron status was investigated in 60 adults with sickle cell anemia as determined by stainable iron in bone marrow aspirates, serum ferritin, serum iron, and the total iron-binding capacity. Seventeen patients (28%) were found to have absent bone marrow iron. There was an excellent inverse correlation between serum ferritin and the serum transferrin (p less than 0.001), and a significant positive correlation between serum ferritin and transferrin saturation (p less than 0.005), bone marrow iron (p less than (p less than 0.001), and history of prior blood transfusion (p = 0.005). Results of complete radiologic examination of the gastrointestinal tract and proctoscopy were negative in the 17 patients in the iron-deficient group. The high incidence of iron deficiency may be related to excessive urinary losses of iron. Our data indicate that serum ferritin values of less than 30 ng/ml are diagnostic of iron deficiency in patients with sickle cell anemia, with a high degree of specificity (98.7%). However the sensitivity of the test at a serum ferritin level of 30 ng/ml is only 32%. The diagnostic evaluation and the management of sickle cell anemia in iron-deficient patients needs to be better defined.