A phase II trial of intermittent high-dose recombinant interleukin-2 (rIL-2) was initiated to evaluate the response rate, remission duration, and toxic effects in patients with measurable metastatic renal cell carcinoma. The rIL-2 was administered as a bolus intravenous infusion at a dose level of 10.0 x 10(6) U/m2 three times weekly, preceded by indomethacin (50 mg orally). Dose reductions of rIL-2 for hypotension and other grade 3 or 4 toxic effects were permitted. Forty-four patients were entered and 41 were eligible. Previous treatment included nephrectomy (23 patients), radiation therapy (seven), and hormone therapy (three). Most toxic effects observed were moderate and included nausea, vomiting, anorexia (85%); hypotension (85%); fever, chills (78%); central nervous system changes (24%); myelosuppression (27%); and creatinine elevation (15%). Four instances of grade 4 toxicity were observed and included nausea, vomiting with dehydration; hypotension; and myocardial infarction. Thirty patients (73%) required dose adjustments because of toxicity. Five responses (12%) were seen, which included one complete and four partial. Sites of response included lung, liver, and soft tissue; the duration of response ranged from 2 to 20+ months. These results demonstrate that this schedule of rIL-2 can be administered in an outpatient setting, and can produce tumor regression in patients with metastatic renal cell carcinoma, including durable complete responses.