Acute idiopathic thrombocytopenic purpura often undergoes spontaneous remission, especially in the young. In patients with chronic conditions complete remissions are unusual. Splenectomy is a recognized therapeutic measure for the cases that fail to remit. However, in about 50% of adults and 10% of children, neither corticosteroids nor splenectomy is satisfactory. Long-term steroid therapy may have many undesirable and sometimes dangerous side effects. The immunosuppressive drug azathioprine (Imuran) was used in long-term management of refractory idiopathic thrombocytopenic purpura in eight cases. Three patients had undergone splenectomy with no improvement in their condition, and all had long-term corticosteroid therapy previously with occasional disastrous results (diabetes mellitus in two instances, collapsed vertebra in one, and psychic disturbance in another). Following the use of azathioprine, the results in seven of the eight patients were satisfactory.