The identification of tumor markers in patients who had undergone operation for breast cancer provides important information in the follow-up in addition to evaluation by clinical and visual methods. The aim of our study was to determine the clinical prospective value of CA 15-3, mucin-like carcinoma-associated antigen and carcinoembryonic antigen in preoperative measurement of serum samples in patients with primary breast cancer, and to determine CA 15-3 and steroid receptors in the cytosol of the tumor. The results show that the most exact correlation occurred between serum CA 15-3 and the different stages of the tumor. However, there is no conclusive evidence for the prognosis and the course of the disease from preoperative findings of tumor markers in serum samples or in the cytosol of the tumor in patients with breast cancer.