Two cases with mitral valve prolapse (MVP), without any other cardiac abnormalities at the initial evaluation, developed the clinical features mimic to dilated cardiomyopathy (DCM) during follow-up period. Case 1. A 40-year-old man visited our hospital in May 1982 to evaluate a heart murmur. A standard 12-lead electrocardiogram (ECG) showed an abnormal Q wave in lead III. Echocardiography revealed MVP, but neither dilatation nor wall motion abnormality of the left ventricle (LV) were observed. Thallium-201 scintigraphy revealed an abnormal thallium uptake at the apex and inferior wall. He had no episode of acute myocardial infarction or myocarditis, but complete right bundle branch block developed, thus, he was hospitalized in October 1984. He had no coronary artery lesions, and had only mild mitral regurgitation on left ventriculography. The motion of the interventricular septum and apex was reduced on echocardiogram and a persistent perfusion defect was observed at the inferior wall and the interventricular septum on Tl-201 scintigrams. In December 1985, he experienced an Adams-Stokes attack due to complete atrioventricular block. Echocardiographically, the left ventricle enlarged, and the wall motion abnormalities and a perfusion defect on Tl-201 scintigrams were relatively severe. Case 2. A 46-year-old woman occasionally experienced palpitation of short duration and chest oppression since 1977. She was admitted to our hospital because of cardiac symptoms in 1982. A heart murmur of Levine II was heard and a standard 12-lead ECG showed single supraventricular extrasystole and T wave inversion in lead III and aVF. Echocardiography revealed MVP and mild mitral regurgitation, but neither dilatation nor wall motion abnormality of the LV was observed. During 6-year follow-up period, permanent atrial fibrillation developed and LV developed dilatation and wall motion abnormalities progressed. Thus, during follow-up periods, DCM-like features developed in two cases who had had MVP as a sole echocardiographic abnormality with systolic murmur and non-specific ECG changes. We consider that these two may be important cases who may show a relation between cardiomyopathic process and MVP.