Nine patients with chronic type B hepatitis were entered into a preliminary study of recombinant, human alpha-interferon therapy. Patients received one to four courses of interferon, each consisting of a fixed dose of 18, 36, 50, 68, or 100 million units given three times a week for 2 wk. Side effects including fever, chills, fatigue, myalgias, headache, and neutropenia were common and especially severe with higher doses. Serum hepatitis B virus DNA polymerase activity fell during therapy to 15%-30% of the pretreatment levels irrespective of interferon dose, but rose to the initial level by 10 days after the course ended. During follow-up, 2 patients had a sustained clinical remission in which hepatitis B virus DNA, DNA polymerase, and hepatitis B e antigen disappeared from serum and amino-transferase activities fell to normal. One patient became hepatitis B surface antigen negative. We conclude that higher doses (50 and 68 million units) of interferon have greater side effects than lower doses (18 and 36 million units), without having any greater antiviral efficacy. Further studies should be directed at therapy with lower doses given over longer periods.