Histological grading is an important parameter for the risk assessment in patients with breast cancer. However, up to now differing grading methods are used which have not been compared with respect to their prognostic significance. In the present study the prognostic significance of three different methods of histological grading (Elston, Contesso, Helpap) was determined in a sample of 292 patients. Furthermore, results obtained in needle biopsies were compared with those obtained in surgical resection specimens in 31 cases. The mitotic counts and the Contesso method were performed on two microscopes with different field areas (0.238 mm2 and 0.345 mm2). Univariate and multivariate analysis revealed that all three histological grading methods had a high prognostic value concerning overall survival (OS) and disease-free survival (DFS). Using univariate and multivariate analysis the Elston method performed best to determine OS and DFS (p<0.0001 and p<0.001). The field area of the microscope had a minor influence on the mitotic count and on the results of the Contesso method. The histological grading was reliable in needle biopsies: the best agreement to grading obtained in the definitive surgical specimen was achieved with the Elston method (kappa statistic 0.727). As a conclusion, we could show that determination of the histological grade is an important prognostic factor in breast cancer with the Elston method giving the best results. Also, we could demonstrate that histological grading in needle biopsies is reliable enough to allow a preoperative risk estimation.