We analyzed the phenotypic distribution of the major T-lymphocyte subsets in the peripheral blood of 22 renal cell carcinoma patients before and after nephrectomy. We also compared these distributions to those of healthy controls and related them to tumor spread. The lymphocyte subsets were analyzed by means of flow cytometry. The CD4+ subset was the only one which was significantly decreased (x +/- SD: 36.2 +/- 6.4 vs 41.4 +/- 2.2 in healthy controls, P < 0.05), this contributing to a significant decrease in the CD4/CD8 ration (x +/- SD: 102 +/- 0.56 vs 1.42 +/- 0.28, P < 0.05). The decrease was more apparent with advanced stage. Helper cell activity increased significantly after nephrectomy in the higher stage patients (x +/- SD: 41.1 +/- 4.6 vs 36.4 +/-3.1 and 38.2 +/- 3.9 vs 30.1 +/- 4.2 for stage T3 and T4 patients respectively). Knowledge of peripheral blood lymphocyte patterns that correlate with various tumor stages and therapies could provide information in host-tumor relationship and predict the clinical outcome and response to therapy.