The serum levels of CA 125 and CA 19-9 were determined by an immunoradiometric assay employing the monoclonal antibody OC 125 and anti-CA 19-9 antibody in 88 patients with ovarian carcinoma. When a cut-off value of CA 125 was set below 35 U/ml in the control group, serum elevated levels of CA 125 were found in 86.7% of the patients with surgically demonstrable ovarian serous cystadenocarcinoma, in 100% (4/4 cases) of clear-cell carcinoma, in 50% (2/4 cases) of endometrioid carcinoma, in 100% (5/5 cases) of undifferentiated carcinoma, and in 80% of the recurrent cases. Using a cut-off value of 37 U/ml, serum elevated levels of CA 19-9 were detected in 68.2% of mucinous cystadenocarcinoma, in 28.9% of serous cystadenocarcinoma, in 75% (3/4 cases) of metastatic ovarian carcinoma, and in 37.5% of the recurrent cases. A statistical analysis of the combination assay using CA 125, CA 19–9, tissue polypeptide antigen (TPA), immunosuppressive acidic protein (IAP), ferritin and CEA was carried out by multivariate method (discriminatory analysis) in 45 patients with ovarian carcinoma and 50 healthy subjects. As a result before treatment, positive rates of a single tumor marker were 79.7% with CA 125, 42.7% with CA-19-9, 73.1% with IAP, 61.7% with TPA, 64.3% with ferritin and 25.4% with CEA, respectively. A combination assay of these markers was useful for detecting identification of ovarian carcinoma, by which it gave a higher accuracy of ovarian cancer detection.