In breast cancer patients the detection of axillary lymph node involvement is a very critical issue, in view of the earlier diagnosis of the disease in recent years, and the increased frequency of very small tumors at first presentation. The size of cancer is related to the risk of axillary metastases, and this may affect the prognosis and the therapeutic strategies. Axillary lymph node involvement is generally recognized as an index of distant microdiffusion, and as it affects overall and disease-free survival, represents the basis for adoption of adjuvant chemotherapy. Routine axillary lymph node dissection (ALND) is expensive, and does not benefit about 70% of early breast cancer patients which are node negative (pN-). Today most of these patients have to sustain the potential morbidity and the economic costs of ALND. The clinical approach is known to be an unreliable diagnostic tool, and for the detection of axillary metastases, conventional X-ray techniques are also unable to solve the problem. By contrast, nuclear medicine procedures have revealed a very interesting diagnostic potential in recent years. This paper analyzes the numerous studies conducted in the field of lymph node visualization and the heterogeneity of the published experiences, taking into account the different approaches proposed in the literature: a) imaging with gamma-emitting tumor seeking agents; b) radioimmunoscintigraphy intravenous (i.v.) or by the interstitial route; c) lymphoscintigraphy with colloids and gamma probe sentinel biopsy; d) positron emission tomography (PET). Although it is very difficult to make a definitive statement about the clinical efficacy of all these methods, this paper reports the most important series of patients examined in the literature as well as the author's own experiences. This can serve as the basis for a better understanding of the potential of nuclear medicine procedures, and gives the reader the opportunity to weigh advantages and drawbacks of each method. At present, lymphoscintigraphy with gamma probe sentinel biopsy and FDG-PET are the nuclear medicine approaches with the best diagnostic performance. However, a correct comparison of the methods will not be possible, until their careful assessment in the same patients is performed. In addition, a final statement today should consider also the increasing need to carry out an economic analysis by evaluating the cost-effectiveness of the examinations.