Introduction: Sentinel Lymph Node Biopsy (SLNB) is the standard of care for staging axillary lymph nodesin women with breast cancer and clinically negative nodes. It is associated with reduced arm morbidity,moderated or severe lymphoedema, and a better quality of life in comparison with standard axillarytreatment. Unfortunately, skip metastases makes all minimally invasive approaches, such as axillarysampling, unreliable. The aim of the present clinical prospective study is to evaluate the position of SLNin an important number of cases and establish the real incidence of skip metastases in clinically nodenegativepatients.Patients and methods: A cohort of 898 female patients with breast carcinoma was considered, from 2001to 2008. Once SLN was localized, by means of radio-colloid or blue dye staining, and isolated, a biopsywas performed. Only those positive for metastases were submitted to axillary dissection.Results: Only in nine cases a SLN was not isolated. We had 819 cases of first level SLN (group A) and 69cases of second level SLN (group B). Considering all of 889 cases, SLN was localized in the second level in69 patients (7.8%); but if we consider metastatic SLN alone (340 cases), it was in the second level in 23subjects (6.8%). In total, we had a positive second level SLN in 2.3% of cases (23/889).Conclusion: Second level SLN could be considered only an anomalous lymphatic axillary drainage and itdoes not linked to particular histological variants of the primitive tumour. In our study, skip metastaseswere recognized in only 2.6% of cases, therefore, whenever a SLN is not isolated for any reason, the firstlevel sampling represent a viable operative choice.