The clinical, anatomic and functional features of 23 pts with congenital mitral valve malformation, seen at the University of Padua over a period of 10 years, are described. All pts underwent hemodynamic investigation and echo-Doppler evaluation. Diagnosis was confirmed at surgery in 17 cases, and at necropsy in six. In 9 pts mitral anomalies determined prevalent stenosis; the remaining 16 pts had moderate to severe mitral regurgitation. Associated cardiac malformations were present in 19 cases (82.6%). The clinical presentation occurred earlier in pts with mitral stenosis (16.9 months vs 6.55 years). The morphologic and echocardiographic features of each malformation are described. The term "valve dysplasia", as proposed by Becker et al to define the non-Ebstein malformations of the tricuspid valve, is herein applied to the congenital anomalies of the mitral valve in order to obtain a uniform and homogeneous approach to this vast spectrum of malformations.