Along with introduction of the objective methods for the study of cardiovascular system the diagnosis of mitral valve prolapse is not difficult. Lack of universally agreed terminology is a major barrier to interpreting studies assessing mitral regurgitation. Terms such as “billowing”, “prolapse”, “partial flail”, “flail”, “myxomatous disease”, “floppy valve”, “Barlow’s disease” and “fibroelastic degeneration” are used interchangeably, often without an effort to distinguish between etiology and lesion, and failing to offer much insight into the valve dysfunction causing regurgitation. This article presents the history of the problem of mitral valve prolapse, classification and definition which was proposed by several authors. It is shown that mitral valve prolapse that is a heterogeneous group of diseases requiring additional research in order to identify groups of patients with an increased risk of progression of prolapse and complications.