During a randomized controlled trial of interferon and descyclovir therapy, the beta 2-microglobulin and SGOT serum levels in 36 patients with chronic HBe-positive hepatitis B were studied in order to determine whether beta 2-microglobulin has prognostic value for HBe seroconversion. Pretreatment levels of beta 2-microglobulin were elevated in 39% of patients. Significant differences in mean beta 2-microglobulin activity and mean SGOT between treated patients and untreated controls were observed after 4 and 8 weeks of treatment (P less than 0.05). Levels in control patients remained stable. Prior to and during therapy, the mean elevation of beta 2-microglobulin and SGOT levels was similar in responders (N =7) and non-responders (N = 11). The outcome of antiviral therapy in our patients was not dependent on beta 2-microglobulin levels measured before or during interferon therapy.