Six tumor-associated antigens, cancer antigen 125(CA125), tissue polypeptide antigen (TPA), ferritin (Fr), carcinoembryonic antigen (CEA), alpha fetoprotein (AFP), and sialyl Lex-i(SLX) were measured simultaneously for the early detection of ovarian cancer. To decrease both false positive and false negative cases in the combination assay, the value of statistical discrimination analysis employing the serum values of appropriate tumor markers in detecting ovarian cancer was studied by the method of Mahalanobis' generalized distance. The new "ovarian cancer screening test" designed by us has been enforced in Shizuoka Prefecture since 1988, and 23,307 serum samples have been analyzed. Of the 165 ovarian cancer patients 127 patients were suspected as cancer by such clinical procedures as pelvic examination and/or ultrasonography, while 150 patients were detected cancer by the statistical discrimination method. Of the 38 patients with ovarian cancer overlooked by the clinical procedures 31 could be found by the statistical method. We conclude that clinical procedures and the statistical method can be complementary in detecting patients with this malignancy.