Interferon alpha is the only available therapy for patients with chronic hepatitis B. With interferon alpha 3-15 MU thrice weekly or 5 MU daily during 3-6 months one-third of the patients achieve seroconversion of HBeAg and HBV-DNA together with normalization of aminotransferases and slight improvement of histology. Loss of HBsAg is reported in a minority of responders during treatment, but increases during follow-up. Patients with baseline alanine aminotransferase of at least twice the upper limit of normal and low HBV-DNA concentration achieve the best response rates. HIV-positive patients with low CD4 counts and Asians are poor responders. As side-effects influenza-like symptoms are experienced by almost all patients. Mild leukopenia, thrombocytopenia and decreased hairgrowth are frequently reported. Severe depression, depersonalization and psychosis are reported in a small number of patients but tend to be poorly recognized in some studies. The decision whether dose reduction is indicated seems strongly related to the opinion of the investigator. Although long-term effects on the occurrence of cirrhosis and the development of hepatocellular carcinoma are not available yet, the achieved results are promising.