A cohort of patients with chronic type B hepatitis has been followed regularly with frequent determinations of routine serum biochemical liver tests as well as serologic markers of hepatitis B viral infection. Selected patients have been entered into therapeutic trials in which antiviral or immunomodulating agents have been administered. A randomized, controlled trial of a four month course of alpha interferon has been conducted in 45 patients with chronic type B hepatitis. Patients were randomized to receive A) 5 million units (mu) of interferon subcutaneously daily, B) 10 mu of interferon subcutaneously every other day, or C) no therapy. To date all 45 patients have been followed after the four month trial for 3 months and 25 for 1 year. Clinical and serological remissions in chronic type B hepatitis have occurred in 10 of 31 (32%) treated patients and in 2 of 14 controls (14%). Thus, remissions of disease occurred in twice as many treated patients as controls. This difference, however, is not statistically significant (p = 0.185). The apparent beneficial responses to prolonged interferon therapy are encouraging, but the low rate of response suggests that satisfactory therapy of chronic type B hepatitis may require the administration of combinations of alpha interferon with other antiviral or immunomodulatory agents. In this context, preliminary studies are being undertaken to evaluate a new antiviral compound called BW-A515U or 6-deoxyacyclovir in a small number of patients with chronic type B hepatitis.