The sentinel node procedure has increasingly been used as a diagnostic tool for staging breast cancer. Although many institutes have embraced this procedure, many issues concerning the indications and the technique itself remain unsolved. In this review, several aspects regarding these controversies are discussed from the perspective of The Netherlands Cancer Institute. These include the definitions used to identify the sentinel node, the indications and contraindications for this procedure and the injection site of the tracer and blue dye. What are the clinical implications of a micro-metastasis in the sentinel node? What is the best treatment for patients with an involved axillary node? Should non-axillary sentinel nodes be pursued, and if so, what are the implications for further management of these patients? Finally, the current TNM system is discussed in perspective of the evolving sentinel node procedure. Although many questions remain to be solved, the regional recurrence rates are low when axillary clearance is omitted because of a tumor-free sentinel node.