The aim of this study was to evaluate the efficacy of human lymphoblastoid interferon (Wellferon) in the treatment of chronic hepatitis B virus (HBV) infection. To date 70 patients have entered the study, 33 randomized to receive interferon at doses of 5 MU/m2 i.m. daily for the first 4 weeks and three times weekly for 5 months thereafter and 31 acted as controls. Seventy-nine per cent of the treated group permanently cleared HBV DNA compared with 48% of the control group (p = 0.01): 69% of the treated patients and 38% of the controls who eliminated HBV DNA cleared HBeAg, HBeAb (p = 0.02). Twenty-four per cent of the treated patients and 3% (p = 0.01) of the control group had clearance of HBsAg and seroconversion to HBsAb. From these results it was concluded that interferon had a therapeutic effect on Italian heterosexual patients with chronic hepatitis B viral replication.