Tumour markers are putative prognostic indicators for patients with breast cancer, but have not been elevated independently by multivariate analysis in a large patient number. In 550 patients with breast cancer without known metastases the levels of the serum tumour markers CEA und CA 15-3 were determined preoperatively and during follow-up. The prognostic relevance of these markers for recurrence (n = 128/487) and death of disease (n = 55/550) was evaluated in relation to established prognostic factors. In univariate analysis tumour size, lymph nodes, histological grading, age, hormone receptors, preoperative value of CEA (cut-off 2 ng/mL) and CA 15-3 (cut-off 25 U/mL) and their decrease of more than 33% within seven months after operation were significant for relapse. The results for death of disease were similar except for age. In multivariate analysis tumour size, lymph nodes and decrease of CEA > 33% (p < 0.001) were independent prognostic factors for recurrence. For overall survival tumour size, lymph nodes, histological grading and preoperative levels of CEA > or = 2 ng/mL (p = 0.038) and of CA 15-3 > or = 25 U/mL (p = 0.007) were independent prognostic factors. Pre- and postoperative values of the tumour markers CEA und CA 15-3 are strong independent prognostic factors for relapse and survival in breast cancer patients.