In order to determine whether tumor-infiltrating mononuclear cells (TIM) of renal cell cancer (RCC) is suitable for adoptive immunotherapy, their number and characteristics were examined immunohistologically. TIM consisted of T cells and a smaller number of macrophages. Among T cells, CD8-positive cells were the dominant population which was reported to be more potent for the lysis of tumor cells. The number of T cells was variable: in 5 tumors no T cells were observed and in an other 5 the number of T cells were less than 2 x 10(6) cells/cm3. These results suggest that the TIM of RCC might be favorable for adoptive immunotherapy but TIM could not be available in some cases because of their small number.