Thirteen patients with classical Friedreich's ataxia underwent cardiac catheterization with recordings of retrograde cardiac pressures, measurements of cardiac output and calculation of the left ventricular volumes and mass. The cardiomyopathy in Friedreich's ataxia falls into the hypertrophic group of cardiomyopathies with decreased compliance of ventricular myocardium, varying degrees of concentric and asymmetric hypertrophy and outflow tract obstruction. Although there is no clear parallel between the degree of abnormal hemodynamic findings and the degree of neurological impairment, severely handicapped patients may present a diffusely hypertrophied and hypokinetic left ventricular myocardium.