Clinical and echo-phonomechanocardiographic reports. The results concerning 7 subjects with mitral valve prolapse (M.V.P.), all members of the same familiar group, are reported. The anamnestic investigation for cardio-vascular deseases, Marfan's syndrome or other abnormalities referred to mesenchimopathies has been negative. No subject with M.V.P. has referred subjective cardio-vascular symptoms nor radiological, ecgraphic and echo-phonomechanocardiographic signs of reduced cardiac function, have been pointed out. The phonomechanocardiographic tracings have shown a variable and low-amplitude click. The echocardiographic tracings have shown a U-shaped (3 cases) and double U-shaped (1 case) pansystolic, early systolic (2 cases) and of doubtful classification (1 case) prolapse. The hypothesis of an autosomal dominant form of inheritance of the desease with not yet clear mechanism of genetic transmission is confirmed. Furthermore, environmental and genetic factors that interfere with the orderly valvular formation at a certain stage of the fetal development, are referred. The Authors remark the necessity of further investigations, among more familiar groups, for identifying the genetic-environmental factors, that, eventually, could have any implication in the ethiopathogenetic mechanism of the disease. The report of "silent" forms and the not yet completely known evolution of the M.V.P. don't justify its not-recognition.