Interleukin-2 (IL-2), given subcutaneously with interferon-alpha, induces clinical results similar to those achieved with intravenous administration in advanced renal cancer but with lower toxicity. This study was performed to investigate the efficacy of IL-2 subcutaneous therapy alone in advanced renal cancer patients pretreated with interferon-2 alpha. The study included 13 evaluable patients, 6 of whom had visceral metastasis sites. The cycle consisted of IL-2 at 9 x 10(6) IU/m2 twice daily for 2 days, followed by 1.8 x 10(6) IU/m2 every 12 h for 5 days/week for 6 weeks. Clinical responses were: partial response: 4(31%); stable disease: 7(54%), progressive disease: 2(15%). The median duration of response was 9+ months (range 6(+)-12+). Toxicity was low in all patients, and in particular no important cardiovascular side-effect was seen. The results of this study show that IL-2 subcutaneous therapy alone is an effective and well tolerated treatment in advanced renal cancer patients progressed under interferon-alpha therapy.