Escalating doses of recombinant human interleukin-2 (rIL-2) were combined with long-term cultured rIL-2 activated killer cells to treat patients with disseminated melanoma, renal cell cancer, and colon cancer. Twenty-four patients were entered, 12 with renal cell cancer, 8 with colon cancer, and 4 with melanoma; 23 were evaluable for efficacy and toxicity. The (dose-related) toxicities were moderate to severe and consisted of fever, chills, rigors, weight gain, hypotension, mild confusion, elevation of liver enzymes and serum creatinine, thrombocytopenia, and eosinophilia. No cardiac events (arrhythmias or myocardial infarction) were recorded. None of the patients were admitted to the intensive care unit, and no deaths occurred. Two partial responses were observed, one at relatively low doses of rIL-2 in a patient with renal cell carcinoma and one at the highest dose level in a patient with malignant melanoma. The maximally tolerated dose level of rIL-2 for this study was 6 X 10(6) U/m2 i.v./day. The recommended dose for further studies is 3 X 10(6) U/m2 i.v./day in three divided doses.