Coexistence of ovarian cancer and renal cell carcinoma (RCC) is extremely rare. Only one case was diagnosed in a total of 584 patients with RCC from 1982 to 2002 at our hospital. A 58-year-old woman presented with an enlarged girdle length for 3 months. Computed tomography scan showed a right cystic adnexal mass measuring 10 x 10 cm, and another tumor measuring 3 x 2 cm at the right kidney. She underwent debulking surgery and radical nephrectomy. Pathologic examination revealed right ovarian clear-cell carcinoma with peritoneal, omental, and fallopian tube metastasis, and conventional clear-cell renal carcinoma. RCC was strongly positive in epithelial membrane antigen (EMA) staining and negative in estrogen receptors (ER), progesterone receptors (PR), 34betaE12 (high molecular weight cytokeratin), and vimentin staining. Ovarian clear-cell carcinoma showed weakly positive results in EMA staining and negative results in ER, PR, 34betaE12, and vimentin staining. Although chemotherapy was given, the patient died of disseminated ovarian cancer metastasis 20 months after operation. In conclusion, coexistence of RCC and ovarian cancer is rare and the pathogenesis remains to be clarified.