Sentinel lymph node (SN) biopsy is a recently developed, minimally invasive technique for staging the axilla in breast cancer. This new procedure of selective lymphadenectomy has been the subject of several studies, but there is not currently a consensus of opinion to define which is the best method of identification. At the Institut Curie since 1996, we have been using the Patent blue dye. The current series present the result of 122 patients with T1, T2, N0 or N1a breast cancer consecutively operated between december 1997 and august 1998. Sentinel nodes were identified in 107 out of 122 (87.7%) and accurately predicted axillary nodal status in 104 out of 107 (97.1%) cases. Three out of 35 node positive patients would have been missed with sentinel node biopsy alone, for a false negative rate of 8.5%. In all 3 cases, one lymph node presented with a micrometastases. In 15 cases out of 35 with metastatic axillary nodes, the only positive node was the SN (43%). The encouraging results of this study shows that it is possible to identify, in a large number of cases, the sentinel node by means of Patent blue dye only. This article detailed the technique used and reviews the literature concerning other methods of identification.