A dynamic immuno-enzymatic assay of CA 125 was carried out in 43 patients (230 tests) with ovarian tumors receiving chemotherapy alone (group 1), surgery + adjuvant chemotherapy (group 2), or neoadjuvant chemotherapy + surgery + adjuvant chemotherapy (group 3). Mean concentration of CA 125 before treatment was 1,635.0 (362.8 Unit/ml. Direct correlation between number of cases with normal level and that of chemotherapy courses received was established in group 1. After 4-7 courses, the antigen level came back to normal in 80.0%. However, chemotherapy alone failed to bring the marker concentration down below 5.0 Unit/ml, which is believed to promise favorable prognosis. In group 2, CA 125 came back to normal after adjuvant chemotherapy in all patients. The best results in that group were obtained following 3 courses: 5.0 Unit/ml--41.7%, and < 10.0 Unit/ml--75%. Additional 1-3 courses failed to improve the results. Normal concentration was reported after first-line adjuvant chemotherapy in 63.6-75.0% in group 3. The best results after a second course of adjuvant chemotherapy were: > 5.0 Unit/ml--12.5%, and > 10.0 Unit/ml--56.3%.