Human recombinant interferon-α2C was given to 4 patients with essential thrombocythaemia. Three patients achieved a complete remission on day 19 ± 1 and the 4th achieved a partial remission. After 4 weeks of induction therapy, a maintenance therapy of twice weekly intramuscular injections of 5 × 106 or 10 × 106 IU was instituted but did not maintain the remission.