We describe a case of a 34-year-old male patient first hospitalized in February '93 for stroke (concomitant dilated-hypertrophic cardiomyopathy was noted), and then in April '93 for congestive heart failure. The presence of myopathy, encephalopathy, lactic acidosis and stroke episode allows for the diagnosis of MELAS syndrome, proven by a specific point mutation in mitochondrial DNA. In this case we were able to observe not only the electrocardiographic and echocardiographic features of hypertrophic cardiomyopathy, previously described in mitochondrial encephalomyopathies, but we were also able to monitor the rapid evolution of this cardiomyopathy towards the hypokinetic dilated form with severe impairment of systolic function; this transition was due to changes in the heart anatomy and structure with reduction in the left ventricular (LV) wall thickness and dilatation of all chambers. The remodeling of LV geometry seems to be not definite and capable of dynamic evolution, as suggested by clinical and echocardiographic findings evaluated six months after the hospitalization. In this patient, we obtained a mid-term favourable clinical outcome using inotropic drugs and Ubiquinone (coenzyme Q), an intermediate substrate of the energetic metabolism, which seems to be poorly synthetized because of the early enzymatic defects in the mitochondrial respiratory chain.