Six patients with chronic type B hepatitis and concurrent infection with the immunodeficiency virus were treated with 600 mg azidothymidine (AZT)/day and 3 X 10(6) units of interferon-alpha (IFN-alpha) every other day for a total of 4 months. None of the patients treated lost the hepatitis B virus (HBV). HBV-DNA concentrations were not significantly influenced by this treatment. Human immunodeficiency virus (HIV) infection was also not affected except for a transient rise in CD 4-positive cells in 2 individuals, who had initially low CD 4-positive cells. Treatment did not influence the presence of HIV-Ag in the serum. In conclusion, a combination therapy of IFN and AZT does not seem to be beneficial at the doses given and the time involved.