Major histocompatibility complex (MHC) antigens and intercellular adhesion molecule-1 (ICAM-1) play important roles in immune response. In order to investigate the association between renal cell cancer (RCC) and host's immune system, expression of MHC antigens and ICAM-1 was examined on RCC. Immunohistochemical analysis revealed a positive correlation between the expression of MHC antigens and ICAM-1. In general, tumor with higher degree of mononuclear cell infiltration expressed MHC antigens and ICAM-1 more frequently and intensely. Among cytokines which were reported to be potent inducers of ICAM-1 on malignant melanoma cell lines, interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha augmented the expression of ICAM-1 on ACHN cells whereas ICAM-1 and class I antigens on KRC/Y cells. IFN-alpha enhanced MHC class I antigens but not ICAM-1. Class II antigen expression of both cell lines was augmented by only IFN-gamma. These results suggest that cytokines which could be produced by tumor-infiltrating mononuclear cells, especially IFN-gamma and TNF-alpha, might modulate expression of MHC antigens and ICAM-1, and influence host immune response against RCC.