Sixty-eight patients with moderate (n = 15) or severe (n = 53) aplastic anemia were entered into a prospective, randomized, two-arm treatment study comparing antihuman thymocyte globulin (ATG), lower-dose methylprednisolone (LDM) and oxymetholone to ATG, higher-dose methylprednisolone (HDM), and oxymetholone. There were no differences between the two groups when comparing age, sex, etiology of aplasia, disease duration, severity of aplasia, or pretherapy granulocyte counts. Side effects of LDM and HDM were similar. Of the 64 patients evaluable for response to therapy, 12 of 33 (36%) who received LDM had complete, partial, or minimal responses compared with 15 of 31 patients (48%) who received HDM (P = .33). Actuarial survival at 4 years is 43% for patients in the LDM group and 47% for patients in the HDM group (P = .99). Causes of death included hemorrhage, infection, evolution to acute leukemia, and complications of subsequent bone marrow transplantation. Long-term complications included paroxysmal nocturnal hemoglobinuria (n = 3), evolution to myelodysplasia or acute leukemia (n = 6), and recurrent aplasia (n = 6). We were unable to show a significant difference in toxicity, response rate, or survival for patients treated with ATG, oxymetholone, and LDM compared with patients who received ATG, oxymetholone, and HDM.