Renal cell carcinoma (RCC) has been shown to be immunologically more labile than other types of cancer. In this study, we examined tumor necrosis factor alpha (TNF alpha), interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) production of peripheral blood monocytes in 38 RCC patients. Monocytes were isolated from peripheral blood mononuclear cells by adherence to a plastic dish and cultured with lipopolysaccharide for 24 hours. The culture supernatant was obtained, and the production of TNF alpha, IL-1 beta and IL-6 was measured by ELISA. As a result, TNF alpha and IL-1 beta production was significantly higher in the high stage patients compared to the control subjects and low stage patients. When the patients were divided according to serum C-reactive protein (CRP), TNF alpha, IL-1 beta and IL-6 production was significantly higher in the CRP-positive patients compared to the control subjects and the CRP-negative patients. Overexpression of these cytokines may therefore induce a hypermetabolic status that may be a cause of malnutrition and cancer cachexia.