We aimed to evaluate the long-term effect of interferon-alfa(Ifh-alpha.) on chronic type B hepatitis. We treated 39 patients with Ifn-alpha 2a for 4-6 moths with various doses. The patients were followed-up for, at least, 18 months untreated:. Tell of 39(26%) were carrying antibodies against delta agent. In 14 of 29 delta negatives, HBeAg was present in circulation. The other 15 were HBV-DNA +ve, and HBeAg -ve. Five of 14(36%) HBe +ves, and 8 of 15(53%)HBe -ves responded. None of the 10 anti-delta +ves responded. 2/5(40%) from HBe + group, and 4/8(50%) from HBe -ve group relapsed. The overall sustained response rate was 21% in tile HBe +ve, and 27% in tile HBe -ve group. It was concluded that Ifn-alpha treatment achieves all overall sustained response rate of 24% in chronic type B hepatitis uncomplicated by delta agent. Patients with delta superinfection, invariably, do not respond to conventional treatment.