Serum CA125 measurement has an established role in monitoring epithelial ovarian cancer patients, assisting in determining response to chemotherapy and providing a lead time to clinical relapse. Over the past few years there has been a decrease in the use of second-look laparotomy to determine response; however, this is largely due to the lack of impact that this procedure has on survival rather than the growing use of less invasive scanning techniques or CA 125 assay to determine disease status. The value of a marker lead time depends ultimately on a patient's remaining therapeutic options; the influence on survival of therapeutic intervention at pre-clinical diagnosis of relapse remains to be tested in a randomized controlled trial. The third area where CA 125 may help patient management is in predicting progression-free survival and overall survival. Treating patients with aggressive chemotherapy regimes would not be justified (given the deterioration in the quality of life for a period of months that may result from such therapy) if a poor outcome could be predicted. Deciding when to stop ineffective treatment is extremely difficult for the clinician given patients' desire for active therapy. The prognostic value of CA 125 needs to be further clarified before it can influence such treatment decisions. The aim of this study was to help clarify the role of CA 125 in patient management and to assess several other putative EOC markers, including determinants found on the polymorphic epithelial mucin (PEM)--the most promising alternative marker protein to date.