A long-term follow-up report is given on three children with stress-induced bursts of ventricular activity, occasionally proceeding to ventricular fibrillation causing syncope. All patients were treated with a beta-blocking agent as prophylaxis for 12, 10 and 6 years, respectively. Case 1 has no signs of organic heart disease. She has been followed from the age of 8 years and had her last syncope in 1974. She was last seen in Nov. 1976, doing well at the age of 20. Case 2 started having syncopes after an attack of measles at the age of 8 years, at which time she probably acquired some damage to her myocardium. She had persistent bradycardia but no other signs of heart disease. She had an uneventful pregnancy and delivery in 1973 and gave birth to a normal child. She died suddenly in 1974, at the age of 22, four years after her last syncopal attack. Case 3 had cardiomyopathy with increasing heart size and exertional dyspnoea and marked ischaemic ECG changes during exercise. He was followed from the age of 7 years. He died suddenly in 1974 at the age of 16, four years after his last syncope.