A case of renal cell carcinoma with extremely high serum carcinoembryonic antigen (CEA) levels is presented. A 57-year-old female complained of left flank pain. Computerized tomographic (CT) scan revealed left renal tumor and laboratory examination revealed an extremely high serum level of CEA (815 ng/ml). No abnormal findings were recognized in gastrointestinal or genital systems. Radical nephrectomy was done. The histology was renal cell carcinoma (RCC, intermediate type, mixed type, pleomorphic cell type, G3 > G2, INF gamma, pT2, pV0). Tumor cells were positive for CEA by ABC-peroxidase staining. Levels of tumor markers decreased after operation. However, CEA levels rose again and lymph node metastases appeared. She died 6 months after operation.