Many circulating markers are already in clinical practice and in experimental use for the diagnosis, therapeutic monitoring, and in the follow-up of ovarian cancer. The cancer antigen-125 (CA-125) has shown to be useful in epithelial ovarian cancer, but its specificity is too low for the test to be used as a primary screening technique in early stage and particularly in premenopausal women. In the last few years, several studies have focused on using the serial measurement of complementary serum markers to improve the positive predictive value and diagnostic accuracy. The main problem is that the different cellular lines express these markers in a very variable way.