This paper reports a case of dilated phase in hypertrophic cardiomyopathy with mid-ventricular obstruction. Following the first cardiac catheterization and endomyocardial biopsy, the patient was diagnosed as having hypertrophic cardiomyopathy (HCM) with mid-ventricular obstruction. He had been first diagnosed at the age of 38 years and was subsequently followed for 20 years. Echocardiogram revealed gradually progressive dilatation of the left ventricle, associated with disappearance of the mid-ventricular obstruction. The second cardiac catheterization and endomyocardial biopsy performed at the age of 58 disclosed that the patient was in the dilated phase of HCM with a dip-and-plateau pattern diastolic pressure trace.