The frequency and characteristics of cardiac involvement have been evaluated in 22 patients with Friedreich's ataxia and in 10 patients with non Friedreich's ataxia (Strumpell-Lorraine 5 cases; Pierre Marie 5 cases), classified according to the severity and the lasting of neurological disease. In a high percentage (45%) of patients with Friedreich's ataxia, the results show left ventricular hypertrophy as proved echocardiographically by an increase of the interventricular septum thickness and of the posterior wall thickness. On the contrary, no patient with non Friedreich's ataxia had left ventricular hypertrophy. In the patients with Friedreich's ataxia, left ventricular hypertrophy was of concentric type in 27% of the cases and of asymmetric type in 18% of the cases; left ventricular systolic indexes were not reduced. The left ventricular end-diastolic diameter was normal in all the patients. Furthermore, in 4 patients with Friedreich's ataxia (18% of the cases) without left ventricular hypertrophy, mitral valve prolapse has been found. No correlation exists between the severity and the lasting of neurologic disease and the presence of cardiac hypertrophy. This supports the hypothesis that the cardiac abnormality is a primary expression of a genetic defect and not a secondary manifestation of spinocerebellar degeneration. It is therefore necessary to always consider a patient with Friedreich's ataxia as affected with a cardiac disease even if it is not clinically evident.