Ten patients with Friedreich's ataxia were reexamined at a five-year follow-up with electrocardiography and echocardiography. The three patients who initially had had the smallest left ventricular diastolic dimensions relative to their body surface areas (decreased 23% to 25% below predicted dimensions) had undergone dilatation of their left ventricles and atria, with decreasing fractional shortening of the left ventricle, but stable to decreasing ventricular wall thickness. The other seven patients, whose ventricular diastolic dimensions were initially closer to those predicted for their body surface areas, had not undergone significant dilatation. However, their left ventricular posterior walls and interventricular septa had thickened at a mean rate of 0.019 mm/mo. The interplay of these tendencies to hypertrophy and dilatation may explain the disagreement about the type of hypertrophic cardiomyopathy in Friedreich's ataxia.