Thirty-two adult patients with sickle cell anemia were evaluated endocrinologically. Secondary sex characteristics were abnormal in 29, and eunuchoidal skeletal proportions were present in all except one. The age at which different stages of pubic hair growth were attained in these patients was delayed in comparison to normals (P < 0.005). Hormonal assays were carried out in 14 patients. Basal serum testosterone, dihydrotestosterone and androstenedione values were lower (P < 0.02) in patients than controls. Serum LH [luteinizing hormone] and FSH [follicle-stimulating hormone] levels before and after stimulation with gonadotropin-releasing hormone were consistent with primary testicular failure. Erythrocyte and hair Zn concentrations were significantly decreased, and there was positive correlation between erythrocyte Zn and serum testosterone (r = 0.61, P < 0.01) in sickle cell anemia. Androgen deficiency in this disease is a result of primary rather than secondary hypogonadism. Further studies are required to establish the role of Zn in the pathogenesis of testicular failure in sickle cell anemia.