OBJECTIVE In a randomized phase II study we evaluated response, survival and side effects of low dose recombinant interferon-gamma in 30 patients (group 1) versus recombinant interleukin-2 and interferon-alpha 2b in 30 (group 2) with metastatic renal cell carcinoma. METHODS Group 1 received 200 micrograms interferon-gamma subcutaneously once a week. Group 2 received 4 x 4.8 x 10(6) IU/m.2 interleukin-2 subcutaneously on days 1 and 22, 2 x 4.8 x 10(6) IU/m.2 on days 2 and 23, and 2 x 2.4 x 10(6) IU/m.2 combined with interferon-alpha 2b subcutaneously at 3 x 10(6) IU/m.2 on days 3, 5, 24 and 26, and 6 x 10(6) IU/m.2 3 times weekly for 6 weeks. RESULTS Toxicity grades 2 and 3 (World Health Organization) were observed in group 2 only. After followup of 13 months there was no remission in group 1 compared to 7 remissions in group 2, with 23 cases of progressive disease detected. CONCLUSIONS Combination therapy showed an objective response rate of 23% (p = 0.01). Although survival was not a primary aim of the study, there was a tendency toward no significant difference in survival when evaluating these relatively small groups (p = 0.49).