In an effort to correlate the serum values of potential markers, including CA-125, galactosyltransferase, and total sialic acid, with residual tumor mass after initial surgery, 43 patients with FIGO stage lib and c, III and IV ovarian cancer were studied. The sensitivity of galactosyltransferase and siliac acid levels was sufficient to correlate their serum values with the corresponding residual tumor mass. Furthermore, 28 patients were histopathologically evaluated for their response to chemotherapy. Determination of these tumor markers did not permit discrimination between small residual disease (≤1 cm) and a state of ‘no evidence of disease’. Conversely, progression of disease has been associated with a sensitive increase in the level of all three markers. CA-125 has been found to be the most useful of the three for distinguishing between responders and nonre-sponders.