Serum ovarian carcinoma antigen (CA 125) and carcinoembryonic antigen (CEA) were measured in 36 patients with ovarian cancer, to compare their effects and assess clinical applications. The positive rate of CA 125 was significantly higher than CEA, ie, 72.2% v.s. 33.3% in all types of ovarian cancer, 81.3% v.s. 31.3% in the 32 epithelial cancers, and even more of 100% v.s. 25% in the 16 serous cystadenocarcinoma. The positive rate of CA 125 was also higher than CEA in borderline malignancy and stage-I cancers, a possible indication of its greater usefulness in early diagnosis. CA 125 was also a better marker in monitoring of epithelial ovarian cancer than CEA. Combining use of these two markers achieved an even higher positive rate. Therefore it seems useful to utilize them concomitantly in the diagnosis of ovarian cancers.