Objective: The St. Gallen Conference 2011 strongly recommends intrinsic subtyping of breast cancer (BC) for therapeutic decisions. We analyzed the influence of different proliferation assessment methods on the BC subtype distribution. Method: Intrinsic subtyping was performed according to the St. Gallen criteria on 225 BCs. Proliferation was assessed by Mitotic Activity Index (MAI) (area: 1,59 mm², cut-off ≥10) and by several variants of Ki67-Labeling-Index counting any nuclear staining of (1) 100 tumor cells within the hot spot (Ki67-100), (2) 1020 tumor cells in 3 HPF in the tumor periphery, including the hot spot (Ki67-1020periphery), and (3) 1020 tumor cells in 3 HPF, including hot spot, cold spot and an intermediate area (Ki67-1020spectrum) using the recommended cut-off of <14 %. Results: Of 225 carcinomas, 10 % were Triple-negative, 2 % Her2+, 6 % Luminal B Her2+, and 9 % Special Type. The rates of BCs after different proliferation assessment methods were: MAI 49 % vs. 24 %; Ki67-1020spectrum: 34 % vs. 39 %, Ki67-1020 periphery: 24 % vs. 49 % and Ki67-100: 10 % vs. 63 %. Conclusion: Subtyping of Luminal A and Luminal B Her2neg BCs according to St. Gallen 2011 is highly influenced by the method of proliferation assessment used. Its biological relevance seems to be not unequivocal.