The aim of this study was to evaluate the reliability and accuracy of sentinel node biopsy for invasive breast cancer and the predictability of axillary node status. Between January 1996 and June 1997 a total of 73 patients underwent patent blue dye lymphatic mapping and sentinel node biopsy followed by standard (level I and II) axillary node dissection (one bilateral procedure). The sentinel node was identified in 82.4% (61/74) of the cases and was predictive of axillary status in 96.7% (59/61). The false-negative rate of the procedure was 8.0% (2/25). The sentinel node was involved in 37.7% (23/61) and was the only one invaded in 30.4% (7/23). The sensitivity of the procedure was 92% (CI95% 74-99%) and its specificity 100%. It is currently considered to be an attractive new procedure undergoing evaluation in prospective controlled trials. This study confirmed the reliability and reproducibility of intraoperative lymphatic mapping and sentinel node biopsy. This is the first step toward a new era of minimally invasive axillary surgery for breast cancer.