Normocalcemic primary hyperparathyroidism is a new entity which possibly represents a fruste form of the classic clinically symptomatic disease and which has generated a considerable scientific interest in the last decade. Its official recognition is just as recent as in 2008, when an international conference took place for clarifying its nature and relevance (Bilezikian et al., 2009). Its true prevalence is mostly unknown although it is clear that it is recognized more and more in different clinical settings, from internal medicine outpatient clinics to endocrine or rheumatologists consultations. It is a challenging situation for either the clinician and the patient, as therapeutic recommendations are nowadays nor established and different patients may be advised to receive certain active treatment or just follow-up, or even no follow-up. In this chapter the current data in relation to this emergent condition are presented.