Serum tumor markers are useful in diagnosis and follow-up for patients with gynecological malignancy or breast cancer. In epithelial ovarian cancer, CA125 has been identified as the most sensitive marker. Unfortunately, CA125 detection in the serum of patients with minimal malignant tumor has not been possible. Many nonmalignant conditions including endometriosis, menstruation and massive ascites may elevate the CA125, and almost 50% of patients with clear cell adenocarcinoma do not show CA125 elevated above 100 U/ml. To improve sensitivity and specificity in the diagnosis of ovarian cancer, the use of multiple tumor markers and the simultaneous use of image diagnosis should be employed. The value of tumor markers in the screening for cervical cancer and endometrial cancer has received little attention. However, the utility of serum SCC as a marker for monitoring cervical squamous cell carcinoma has been established. Since hCG is produced by gestational trophoblastic neoplasia and is a sensitive marker of trophoblastic cells in the body, patients with choriocarcinoma or invasive mole must be followed closely for this parameter. The improvement of the hCG detection technique has reduced the mortality rate from trophoblastic neoplasia. In breast cancer, many markers including CEA and CA15-3 are used, and they are reported to be useful as markers for monitoring.