Barlow's disease and fibroelastic deficiency are the two dominant forms of degenerative mitral valve disease and have unique differentiating characteristics on clinical and echocardiographic assessment. Preoperative differentiation of patients by both cardiologists and surgeons is important because the techniques, surgical skill, and expertise required to achieve a repair vary among these etiological subsets. Barlow's patients often have multiple complex lesions, thus high rates of repair are only likely to be achieved by a reference mitral valve repair surgeon. In contrast, many forms of fibroelastic disease should be repaired at a high rate by experienced general cardiac surgeons. In this article, we highlight the differentiation of Barlow's disease and fibroelastic deficiency.