Immunosuppressive cytokine, interleukin 10 (IL-10), is associated with progression of the renal cell carcinoma (RCC). However, the roles of its cell surface receptor, interleukin 10 receptor (IL-10R), remain elusive. We quantified IL-10R mRNA expression in paired tumor and non-tumor samples from the surgical specimens of 71 consecutive patients with RCC using a real-time reverse transcription polymerase chain reaction (RT-PCR). The absolute level of IL-10R mRNAs in tumor and non-tumor tissues did not correlate with the malignant and metastatic profiles. The relative yields of the PCR product from the tumor tissue to that from the corresponding non-tumor tissue (T/N) for the expression of IL-10R mRNAs were calculated. A high T/N ratio of IL-10R correlated with poor differentiation (P < 0.001) and metastasis (P < 0.0001). By univariate analysis, a high T/N ratio of IL-10R predicted a shortened overall survival in all cases (P < 0.01). These findings suggest that IL-10R is associated with the progression of RCC.