Thirty-seven patients with pure red cell aplasia (PRCA) were seen between 1966 and 1982. Ten patients had accompanying diseases described in association with PRCA, while the remainder had primary PRCA. All but two patients were treated with some form of immune manipulation, including corticosteroids, cytotoxic drugs, antithymocyte globulin, splenectomy, thymectomy, and plasmapheresis. Twenty-three patients (66%) had a remission induced by immunosuppression. In addition, there were 5 spontaneous remissions (14%). Cytotoxic drugs administered in combination with corticosteroids were the most effective form of treatment, producing 18/32 remissions (56%). Twelve of these remissions were in patients resistant to corticosteroids or in patients who had relapsed while taking them. Thirteen of the 23 patients in whom remissions were induced and one-fifth of the patients with spontaneous remissions have relapsed to date. However, with additional treatment, a second remission was induced in 10/13. Fifty-four percent of the patients with induced remissions remained transfusion-free during most of the follow-up period. Median survival in patients with primary PRCA was greater than 10 yr, whereas in patients with secondary PRCA, it was 4 yr. Infection was a major cause of morbidity and mortality. This study demonstrates the value of a variety of immunosuppressive treatments of patients with PRCA.