CEA, TPA, CA15-3 and BCA225 are the most frequently assayed as tumor markers for breast cancer. The aim of the present study was to reinvestigate the clinical usefulness of these markers in patients with breast cancer (primary: 28, recurrent: 15). In the cases of primary breast cancer, including all stages, positive rates of CEA, TPA, CA15-3 and BCA225 were 18%, 25%, 11% and 18%, respectively, while in the advanced cases of stage III+IV, positive rate of both CEA and TPA increased to approximately 40%. The positive rate of combination assays using four tumor markers was 46% in the cases of primary breast cancer including all stages and was 73% in the cases of advanced primary breast cancer (stage III+IV). In the cases of recurrent breast cancer, the positive rates of CEA, TPA, CA15 3 and BCA225 were 60%, 60%, 67% and 60%, respectively. When all of those tumor markers were used for assays, all of the patients with recurrent breast cancer studied showed elevated serum levels of at least one of these tumor markers. We retrospectively analyzed serum levels of tumor markers in 15 patients who relapsed breast cancer after surgical resection. In 2 patients elevation of some of four tumor markers occurred before the recurrent tumor was detected with RI scintillation and computed tomography. These results suggested that combination assays using CEA, TPA, CA15-3 and BCA225 should be helpful for detecting the recurrence of breast cancer, and also detecting the advanced primary breast cancer.