Right ventricular cardiomyopathy is generally considered a disease with isolated right ventricular involvement, although there are some case reports of concomitant abnormalities of the left ventricle. In order to evaluate the prevalence, characteristics and natural history of left ventricular involvement in this disease, 39 patients with right ventricular cardiomyopathy were studied by 2-dimensional echocardiography. At first evaluation 25 patients (group 1) showed right ventricular abnormalities and a normal left ventricle. In the remaining 14 patients (group 2) the right ventricular abnormalities were associated with left ventricular involvement (asynergic areas and/or mild diffuse hypokinesia). During the follow-up, left ventricular involvement appeared in 6 patients of group 1 and worsened in 4 patients of group 2. Five patients died. Pathological examination (available in 4 cases) showed, at the level of the right ventricle, marked atrophy of myocytes and fibro-fatty replacement, and predominant fibrosis at left ventricular level. Left ventricular involvement is thus frequent in right ventricular cardiomyopathy. At least in some cases the disease appears to be progressive.