CA125 II, an improved version of the conventional CA125 was compared with CA125 as to which was more useful in gynecologic disease. In the diagnosis of tumors around the adnexal field (primary epithelial ovarian cancer, metastatic ovarian cancer, benign ovarian tumor and endometrial cyst), CA125 II showed the same sensitivity and specificity as CA125. CA125 II also has high simultaneous reproducibility in the low concentration area. The examination by the receiver operating characteristic curve revealed that CA125 II has higher precision than that of CA125 when it is used for the screening test. In conclusion, CA125 II is a better tumor marker than conventional CA125.