Five patients with hepatocellular carcinoma were subjected to immunotherapy: three patients were treated by adoptive immunotherapy with lymphokine-activated killer (LAK) cells and recombinant interleukin-2 (rIL-2), and two patients by systemic administration of rIL-2 alone. In one patient with diffuse-type hepatocellular carcinoma and portal vein thrombosis who was treated by infusion of LAK cells (a total number of 1.5 x 10(10) cells/13 doses) and continuous rIL-2 administration (a total dose of 1.25 x 10(8) units) via a percutaneously placed hepatic arterial catheter, the size of the tumor reduced dramatically and the portal vein thrombosis retracted. In two patients who had LAK cells infused (totals of 6.6 x 10(9) cells/4 doses and 3.1 x 10(9) cells/2 doses, respectively) during hepatic angiogram followed by systemic administration of rIL-2 twice a day, no clinical improvement was noticed. In two patients who received rIL-2 alone systemically (total doses of 8.9 x 10(7) and 5.5 x 10(7) units, respectively), neither clinical improvement nor severe side effects were observed. The results suggest that adoptive immunotherapy combined with continuous local administration of rIL-2 via a percutaneously placed hepatic arterial catheter may be an effective therapy without apparent side effects for patients with hepatocellular carcinoma who cannot be treated by conventional cancer therapy.