A pilot study was performed on seven patients with advanced solid neoplasms. They received recombinant leukocyte interferon A (rIFN-alpha A) 12 X 10(6) U/m2 intramuscularly daily for 5 days plus doxorubicin, 25 mg/m2 IV on day 3 of each monthly cycle (Roferon-A, Hoffman-LaRoche, Nutley, NJ). Because of side effects, the dose was not increased above the initial level. There was a striking partial response of biopsy-confirmed hepatocellular carcinoma for 6+ months along with a decrease in alpha-fetoprotein from 39,000 to 202 ng/mL. The doxorubicin dose is approximately 33% to 42% of the typical single-agent dose, thus suggesting that the clinical toxicity from these two agents is additive.