Sentinel node (SN) biopsy in breast cancer is still in a crucial stage of evaluation. Many teams have obtained excellent results using this method, with a detection rate always higher than 90% and a false negative rate between 0 and 8%, in prospective series. The main question is to know if lymphadenectomy can now be avoided when the SN is negative. The answer will come from the results of the two ongoing trials comparing sentinel node biopsy to axillary lymphadenectomy. But their results will be available only in two or three years. However, many teams, as at Institute Gustave Roussy, are now applying the technique routinely, because of the excellent results obtained during their learning curve. But there are some methodological differences between teams, which can influence the detection and false negative rates. Thus, several methodological standards remain to be defined. This review enable us to clarify a certain number of questions. Today, SN biopsy can only be performed by trained teams, with prospective evaluation of their results or participation in phase III trials.