Based on the in vitro and in vivo potentiation of the cytotoxic activity of chemotherapeutic agents by the interferons, a pilot study combining human recombinant alpha-2b interferon (IFN) and doxorubicin was conducted for the treatment of unresectable, histologically proven hepatocellular carcinoma. Between March 1988 and May 1990, 21 patients (median age: 60 years, range: 29-76) entered the study. The dose of doxorubicin was fixed at 35 mg/m2, every 3 weeks. The dose of alpha-2b IFN was 6 million U/m2 per day, 5 days a week. 3 patients (14%) obtained a partial response lasting 11, 16 and 30 months, and 1 had a stable disease during 8 months. The other 17 patients died within a median survival time of 4 months. All patients experienced flu-like symptoms. 7 patients experienced WHO grade III-IV haematological toxicity. We conclude that the association of alpha-2b IFN and doxorubicin is feasible, with respect to the use of doxorubicin at an inferior dose level than the same agent used without IFN. The response rate is comparable to that observed with doxorubicin used alone. Further phase I studies and randomised trials are required to confirm the role of this regimen in the treatment of unresectable hepatocellular carcinoma.