Five-year overall survival after radical surgery in N0M0 renal cell carcinoma varies from 45-80% in pT2 to 35-50% in pT3 categories. In view of the alpha interferon and vinblastine combination which has shown some activity in advanced disease with increasing efficacy in limited metastatic invasion, we decided to explore the theoretical advantage of adjuvant chemo-immunotherapy in radically resected stage II, III renal cell carcinoma. A single-institution phase II study was undertaken to evaluate the efficacy and tolerability of alpha 2a-interferon (alpha 2a-INF) in combination with vinblastine in 30 patients with pT2-T3 N0M0 renal cell carcinoma (RCC). Thirty-two patients who received only radical nephrectomy and extended lymphadenectomy were analyzed and results were compared with the first group. Twenty-three of 30 (76.6%) patients in the first group are alive with no evidence of disease. The median follow-up for the 23 patients still alive was 67 months (range 60 to 72). Metastases were documented in 5 patients (16.6%) with a median interval to progression of 24 months. Four of them (13.6%) died of tumor. In the control group, 16 out of 32 patients (50%) are still alive, with a median follow-up for the patients still alive of 62 months (range 60 to 68). Fifteen patients developed distant metastases and 2 of them had a local recurrence. All of them (46.8%) died of tumor. Median progression interval was 24 months. After stratification by pathological grade, site, laterality and number of nodes found at lymphadenectomy there were no statistical differences in risk of progression or death in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)