Immunotherapy with recombinant interleukin-2 (rIL-2) and lymphokine-activated killer cells (LAK) has become a new form of therapy that has been shown to induce remissions in patients with renal cell carcinoma and melanoma. Despite encouraging results, this form of therapy has been associated with increasing toxicity, often requiring therapy in an intensive-care unit. In this report severe intrahepatic cholestasis occurred in two patients receiving rIL-2 and LAK cells. This form of cholestasis appeared to be directly related to rIL-2 administration at a doses of 2 x 10(6) U/m2 and 3 x 10(6) U/m2 t.i.d. A liver biopsy showed moderate hepatocellular bile stasis, with lobular and portal inflammation. All other studies for potential cause of this cholestasis were negative, including studies for metastatic disease. When therapy was discontinued, evidence for cholestasis and bile stasis resolved. We conclude that rIL-2 is a drug with a potential to induce severe hepatic injury that is reversible upon cessation of therapy with rIL-2. Further care should be exercised when rIL-2 is administered to patients with abnormal liver function.