The aim of the present study was to evaluate the clinical value of the preoperative serum tumour markers TAG 12, CA 15-3 and MCA in predicting a recurrence of breast cancer patients. The sensitivity of the TAG 12 test was 54%, that of the CA 15-3 test 15% and that of the MCA test 15% in predicting a recurrence of breast cancer. The most important predictor of breast cancer recurrence was TAG 12. In order to evaluate the contributions of different tumour marker serum test, a stepwise discriminant analysis was carried out. The discriminant function (DF) is DF = TAG 12 x 0.061 - CA 15-3 x 0.1336 - 0.396. The sensitivity of the DF in detecting recurrence of breast cancer was 63% with a specificity of 90% and an efficiency of 75%. In conclusion, the results indicate that a new tumour marker TAG 12 is superior to CA 15-3 and MCA in predicting breast cancer recurrence. In this study the discriminant function including TAG 12 and CA 15-3 was superior to single preoperative tumour marker tests. The results speak for the use of a decision support system to aid in predicting a recurrence of breast cancer.