To study the distribution of subsets of T cells in renal cell carcinoma, peripheral blood lymphocytes (PBL) and tumor-infiltrating lymphocytes (TIL) were analyzed in 43 untreated patients using two-color flow cytometry. An increase in the relative number of CD4+/CD45RA-, CD8+/CD11- and HLA-DR+/CD3+ cells was shown in TIL when compared with PBL. When the influence of various tumor factors on subsets of TIL was examined, a decrease in CD4, CD4+/CD45RA- and CD16+/CD57- cells and an increase in CD8+ and CD8+/CD11- cells was observed along with the aggravation of tumor stage and grade. In TIL of stage III/IV and grade III/IV disease, most patients showed an increase in CD8+/CD11- associated with a decrease in CD4+/CD45RA- cells, or the reverse, resulting in changes of the CD4+/CD45RA- to CD8+/CD11- ratio. The prognosis for these patients was poor, suggesting that changes in the ratio were a sign of the impairment of local immune status associated with disease progression.