Adoptive transfer of autologous lymphokine-activated killer cells in conjunction with recombinant interleukin-2 in patients with advanced cancer has produced significant regression of metastatic disease in selected patients. We analyzed the effects of interleukin-2 regimens on renal function in 99 consecutive patients. Interleukin-2 therapy with or without lymphokine-activated killer cells was associated with varying degrees of hypotension, fluid retention, azotemia, oliguria, and low fractional sodium excretion. After the patients completed the interleukin-2 regimens, their renal function improved promptly. Renal function values returned to baseline levels within 7 days in 62% of patients, within 14 days in 84%, and within 30 days in 95%. Pretherapy serum creatinine values above 1.4 mg/dL predicted the severity of azotemia and prolonged duration of renal functional recovery, interleukin-2 therapeutic regimens induce prerenal azotemia. Careful selection of patients and early detection of adverse physiologic changes may alleviate the side effects of interleukin-2 therapy.