[en] Aim: The aim of this study is to assess the value of carbohydrate antigen 549 (CA 549) in diagnosis and follow-up of breast carcinoma and compare CA 549 with other tumoral markers. Methods: A. We have studied 1230 determinations of CA 549 corresponding to 460 patients (3 male) with confirmed or suspected diagnosis of breast carcinoma. CA 549 was determined using a radioimmunometric assay that use a 'sandwich' technique on solid phase. B. To compare CA 549 with other tumoral markers we have reviewed the case history of 40 patients with advanced breast carcinoma. The tumoral markers studied were: CEA, CA 19.9, CA 15.3 and CA 549. C. We have performed a correlation study between the different tumoral markers on 124 evaluations and calculated the Pearson's correlation coefficient. Results: In the group of confirmed or suspected diagnosis of breast carcinoma (n=460): 187 patients (40,65%) showed pathological levels of CA 549. In the group of patients with advanced breast carcinoma (36 patients with metastasis and 4 with advanced local extension). the results of the different tumoral markers are presented. The Pearson's correlation coefficient between CA 549 and CA 15.3 was 0.814, while no correlation was found in the remaining markers. Conclusion: CA 549 is a good marker of progression or persistence of tumoral disease in breast carcinoma