The concept of sentinel lymph node biopsy in breast cancer surgery is based on the fact that the tumour drains in a logical way via the lymphatic system, from the first to upper levels. Since axillary node dissection does not improve the prognosis of patients with breast cancer, sentinel lymph node biopsy might replace complete axillary dissection for staging of the axilla in clinically N0 patients. Sentinel lymph node biopsy would represent a significant advantage as a minimally invasive procedure, considering that about 70% of patients are found to be free from metastatic disease, yet axillary node dissection can lead to significant morbidity. Subdermal or peritumoural injection of small aliquots (and very low activity) of radiotracer is preferred to intratumoural administration, and (99m)Tc-labelled colloids with most of the particles in the 100-200 nm size range would be ideal for radioguided sentinel node biopsy in breast cancer. The success rate of radioguidance in localising the sentinel lymph node in breast cancer surgery is about 97% in institutions where a high number of procedures are performed, and the success rate of lymphoscintigraphy in sentinel node detection is about 100%. The sentinel lymph node should be processed for intraoperative frozen section examination in its entirety, based on conventional histopathology and, when necessary, immune staining with anti-cytokeratin antibody. Nowadays, lymphoscintigraphy is a useful procedure in patients with different clinical evidence of breast cancer.