Objective:To observe the expression of CD133 in the clear cell renal cell carcinoma (RCC) and to investigate the related drug resistance.Methods: Flow cytometry and immunohistochemical method were used to examine the expression of CD133 in metastatic RCC cell line RCC05-TXJ, low metastatic RCC cell line RCC05-ZYJ and two clinical non-metastatic RCC primary cultures isolated from a male and a female patient. The four cell lines were treated with IFN-α and 5-FU and the viability of cells were examined by MTT assay before and after treatment.Results: Flow cytometry showed that RCC05-TXJ and RCC05-ZYJ expressed CD133. The in situ carcinomas of male and female patients hardly expressed CD133. Immunohistochemistry examination showed that the local membrane of RCC05-TXJ and RCC05-ZYJ cells expressed CD133. RCC cells of female and male patients hardly expressed CD133. RCC05-TXJ and RCC05-ZYJ cells exposed to IFN-α or 5-FU showed a rebound of survival 24 h after withdrawal of drugs. The survival rates of RCC cells of male and female patients kept at a low level after withdrawal of drugs.Conclusion: There are a small number of CD133+ RCC cells in RCC patients, with a property similar to tumor stem cells, which might be one of the important factors influencing the immunotherapy and chemotherapy of tumors.