The usefulness of tumor markers in serodiagnosis of cancer designed to detect ovarian cancer at an early stage was evaluated from the point of view of their diagnostic value. Namely, eight tumor markers, CA125, SLX, CA72-4, TPA, Fr, CEA, CA19-9, and SCC, were determined and studied to find the combination that would yield the optimal diagnostic value. For this purpose, the diagnostic value was calculated from sensitivity x specificity. As a single tumor marker CA125 proved optimal with a diagnostic value of 0.50. The higher value, 0.53, was obtained as the diagnostic value from the combination of two tumor markers, CA125 and CA72-4. When three tumor markers were combined, CA125, CA72-4 and SLX gave an optimal diagnostic value of 0.65. In the combination of four tumor markers, CA125, CA72-4, SLX and CA19-9 gave a diagnostic value of 0.63. In the five marker combination CA125, CA72-4, SLX, CA19-9 and TPA worked well and had a diagnostic value of 0.59. When the markers were increased to six types, CA125, CA72-4, SLX, CA19-9, TPA and Fr provided a combination with 0.53 as the diagnostic value. In the seven marker combination CA125, CA72-4, SLX, CA19-9, TPA, Fr and CEA gave a diagnostic value of 0.51. The efficiency declined to 0.51 when eight tumor markers were combined. When cost performance in the measurement of tumor markers for early detection of ovarian cancer is taken into account, a dilemma arises in that the increase in the number of tumor markers used is accompanied by higher sensitivity and lower specificity.(ABSTRACT TRUNCATED AT 250 WORDS)