One hundred and fifteen patients with carefully defined Friedreich's ataxia were assessed clinically and electrocardiographically for evidence of heart disease. Cardiac symptoms, of which dyspnoea and palpitations were the most frequent, occurred in less than 30 per cent. Abnormalities on clinical examination were present in a similar proportion; harsh systolic murmurs, ventricular hypertrophy and added heart sounds were the commonest of these. Cardiac failure and persistent arrhythmias were rare and occurred late in the evolution of the neurological disease. Two patients presented with heart disease before developing neurological symptoms. Cardiac signs and symptoms were uncommon in patients without electrocardiographic abnormalities. About two-thirds of the cases had definitely abnormal ECG recordings. The characteristic finding was of widespread T-wave inversion with ventricular hypertrophy. Serial ECGs, recorded over periods of up to 32 years, were available in 30 cases and showed that abnormalities may develop in patients with Friedreich's ataxia at any time up until 20 years after the onset of neurological symptoms. In four patients initial ECG abnormalities had either improved or disappeared subsequently.