The patient was a 46-year-old man with gross hematuria and left lumbar pain. Computed tomography revealed a large left renal tumor with hemorrhage. Serological examination revealed polycythemia and a high erythropoietin level. After left radical nephrectomy, polycythemia and serologically high level of erythropoietin disappeared. Histopathological findings showed renal cell carcinoma composed of spindle cells. Based on the above mentioned clinical course, we diagnosed this case as erythropoietin-producing renal cell carcinoma with polycythemia. It is suggested that erythropoietin not only causes polycythemia but also stimulates proliferation of the tumor, because the majority of erythropoietin-producing renal cell carcinomas have been reported to be highly advanced. This patient had no evidence of disease one year after the operation.