Twenty-four patients with immune thrombocytopenic purpura (ITP) were treated with high doses of intravenous immunoglobulin (Ig). Increase in platelets was observed in all the patients. The maximum value was reached between the seventh and the twelfth day of treatment. The mean number of platelets was 18 x 10(9)/l before the treatment and 150 x 10(9)/l after the treatment. The effect was transient; in fact, a fall in the platelets was observed after 18 days of treatment. Our study confirms that high doses Ig is an effective treatment of ITP, but the high cost and the temporary effect limit its use only in those cases in which other treatments are ineffective or contraindicated.