BACKGROUND Axillary lymph node status is an important determinant of prognosis in breast cancer. However, lymphadenectomy does not benefit half of the patients in whom axillary nodes are free of disease. Sentinel lymph node biopsy is a new technique which allows accurate staging of breast carcinoma without performing total axillary dissection. We describe our experience with the introduction of sentinel lymphadenectomy. METHODS Thirty-seven sentinel lymphadenectomies were performed in 35 patients referred to the Department of Obstetrics and Gynaecology of the University of Berne between December 1997 and June 1998. Mapping procedures were performed using a combination of vital blue dye with preoperative lymphscintigraphy with 99mTechnetium-labelled colloidal albumin and intraoperative use of a gamma probe. Complete axillary lymphadenectomy was then performed in 34 patients. RESULTS One or more lymph nodes were identified in 33 of 37 procedures (89%). With the combination of both localisation techniques the sentinel nodes were identified in all (100%) of the last 19 patients. Sentinel and non-sentinel lymph nodes were always concordant. In this series the negative predictive value is 100% (95% confidence interval: 87.7%-100%). Metastases were found in the sentinel node in 11 of 30 patients (37%). From these 11 patients, 3 (27%) had micrometastases. CONCLUSIONS Histopathologic examination of the sentinel lymph node accurately predicts the axillary lymph-node status. Patients with sentinel nodes free of metastases could avoid the unnecessary peri- and postoperative complications of complete axillary dissection. Further studies are needed to assess whether the improved diagnosis of micrometastases by sentinel lymphadenectomy influences the long-term prognosis of breast cancer.