Factors correlating to mitral annulus calcification (MAC) include risk factors predisposing to atherosclerosis. In patients with mitral valve (MV) prolapse (MVP), other anatomic or mechanical factors have been supposed to facilitate MAC. The aims of this study were, in patients with MVP undergoing MV repair, (1) to describe the prevalence and characteristics of MAC, (2) to correlate MAC with clinical risk factors, coronary involvement, and aortic valve disease, and (3) to describe prevalence, site, and extension of MAC in fibroelastic deficiency (FED) versus Barlow's disease (BD) and correlate MAC to surgical outcomes (repair vs replacement). In 410 consecutive patients with MVP suitable for surgical MV repair, detailed clinical and echocardiographic data were collected to characterize MAC in BD and FED. MAC was found in 99 patients (24%). Age, female gender, coronary artery disease, and cardiovascular risk factors were correlated with MAC. MAC was equally distributed in FED and BD groups despite patients with FED being older with more cardiovascular risk factors. The most common localization of MAC was annular involvement adjacent to P2 (75%), P1 (31%), and P3 (35%). The presence of MAC affected surgical outcomes in both groups (8% patients with MAC underwent replacement after a first attempt of repair vs 3% without MAC). MAC is a common finding in patients undergoing MV repair, and several clinical characteristics correlate with MAC either in FED or BD. In conclusion, despite very high percentage of repairability, MAC influences surgical outcomes and very detailed echo evaluation is advocated.