A total of 37 patients with histologically confirmed chronic viral hepatitis B and presence of HBV-DNA and HBsAg in the serum were treated in a randomized, prospectively controlled multicenter trial either with recombinant IFN alpha-2b alone or a combination of IFN alpha-2b and recombinant IL-2. Twenty-two patients from group A were treated with 3 MU of IFN alpha-2b s.c. thrice weekly for 5 months. Starting at month 2 IL-2 was added: priming doses of 1.5 million CU were given s.c. on the first 2 days of each of the remaining 3 months, followed by maintenance doses of 0.3 million CU daily for 5 days per week. Fifteen patients from group B received 5 MU of IFN alpha-2b s.c. thrice weekly for 5 months. Five patients from group A (24%) and 4 patients from group B (28%) cleared HBV-DNA and HBeAg from the serum, and normalized elevated serum aminotransferase activities. The response rate in both groups did not differ significantly. Since side effects were more pronounced during combination therapy than in IFN alpha-2b monotherapy, it is suggested that treatment with IFN alpha-2b alone is preferable to a regimen of IFN alpha-2b/IL-2 applied according to the above schedule.