Symptomatic immune thrombocytopenia is a life-threatening situation which is conventionally treated in the adult with prednisone, although subsequent splenectomy is frequently unavoidable. Recently, high-dose intravenous gammaglobulin has been reported to be an effective alternative option, particularly in children. To determine the role of this agent in adults a controlled prospective trial has been undertaken. Previously untreated patients with immune thrombocytopenia were randomised to compare oral prednisone (1 mg/kg/day: Group 1: n=13) to high-dose intravenous gammaglobulin (400 mg/kg on days 1 through 5: Group 2: n=7), or a combination of both agents given on the same schedule (Group 3: n=12). The time from diagnosis to commencement of treatment, initial platelet counts, age and sex were comparable in the three groups. At this interim analysis there has been no mortality, but one patient has suffered a cerebrovascular accident. Objective response, defined as a platelet count greater than 50×109/l, was achieved in a median of 5, 5 and 3 days, whereas the time taken to reach peak counts were 9, 5 and 7 days, respectively. The relapse rates, percentage of patients subsequently requiring splenectomy for control of symptomatic bleeding and the postoperative course was comparable between the three groups. These data, although preliminary, re-emphasize differences between the paediatric and adult forms of immune thrombocytopenia and also suggest in the latter patients a need for caution before advocating replacement of prednisone by gammaglobulin as the primary form of treatment.