Thirty three heterosexual chronic hepatitis B virus (HBV) carriers were randomized, with stratification for disease activity, to receive intramuscular recombinant interferon alpha-2a (r-IFN) at doses of 4.5 megaunits thrice weekly for 4 months, or no treatment. During r-IFN treatment, serum HBV-DNA levels fell in all, but 2 patients. Final evaluation at 16 months after randomization revealed that the rate of complete response, i.e., loss of both HBV-DNA and HBeAg with ALT normalization was 22.2% (2 of 9 cases) in patients on interferon and 12.5% (1 of 8 cases) in untreated patients for the group with high serum alanine aminotransferase (ALT) and with piecemeal necrosis on liver biopsy on entry. The corresponding value was 25% (2 of 8 cases) in treated and 12.5% (1 of 8 cases) in untreated patients with low liver disease activity. Overall, a complete response was thus observed in 23.5% of treated patients and in 12.5% of controls. None of the patients on therapy became HBsAg negative. It is concluded that treatment of heterosexual patients with chronic hepatitis B with r-IFN in the dose regimen used here was not associated with a significant higher rate of serologic and clinical response compared to controls, independently of pretreatment biochemical and histologic activity of liver disease.