Background. Macrophage colony-stimulating factor (MCSF) secreted by malignant cells may regulate cell proliferation via an autocrine and paracrine loop, and M-CSF may be useful as a potential tumor marker. We evaluated the diagnostic significance of M-CSF levels in gynecologic patients. Methods. Serum samples were obtained from 20 healthy women and from 102 gynecologic patients undergoing primary laparotomy, and culture media were obtained from cell lines of gynecologic malignancies (oranian cancer, endometrial cancer, cervical cancer, and choriocarcinoma). M-CSF levels were measured by enzyme-linked immunosorbent assay. Results. M-CSF levels in the sera of patients with ovarian cancer and advanced uterine cancer were significantly higher than those in healthy women and in patients with benign tumors (P &lt
0.001). M-CSF levels 7 days after operation were significantly higher than those before operation (P &lt
0.001
paired t-test). But there were no differences between M-CSF levels before and after operation in patients with ovarian cancer. M-CSF levels 3 months after the cessation of treatment had decreased to within the normal range in patients with benign tumor and in cancer patients with no residual tumor. Cell lines of gynecologic malignancies produced M-CSF at various concentrations. Conclusion. These findings suggest that M-CSF, produced not only by cancer cells but also by immune cells in ascites and around tumor tissue and by connective tissue may reflect increased serum M-CSF levels in patients with ovarian cancer, advanced uterine cancer, and benign ovarian tumor, associated with ascites. It seems that operation, because of tissue damage, tissue repair, and various physiological responses, may itself, stimulate M-CSF production.