Following reports that recombinant interferon alfa (rIFN alpha), besides inducing clinical and hematologic remission in polycythemia vera (PV), can also resolve intractable pruritus, we used rIFN alpha to treat 13 PV patients complaining of severe pruritus refractory to conventional treatment (venesection and/or cytostatics). rIFN alpha was administered intramuscularly three times a week at a dosage of 3.0 x 10(6) U. Eight patients (61.5%) reported a > or = 50% reduction of pruritus, which occurred within 2-8 weeks from the start of rIFN alpha treatment, leading to a substantial improvement in their quality of life. Three patients had to stop rIFN alpha within the first month of therapy because of unacceptable side effects. Thus rIFN alpha seems to be capable of providing considerable relief of otherwise intractable pruritus in a good proportion of PV patients.