One hundred forty-nine consecutive patients with tetralogy of Fallot, with or without pulmonary atresia, underwent Blalock-Taussig or Waterston operation for initial palliation. Of these patients, 45 were less than 6 months old, and 63 were less than 1 year old. The type of shunt, and the presence or absence of pulmonary atresia did not have a significant effect (p greater than 0.2) on hospital mortality. Parametric analysis showed a significant effect of age (p = 0.03), the risk of hospital death being 6% at 1 month of age, 4% at 3 months, 3% at 6 months, and 2.5% at 12 months. No late deaths occurred before the age of 3 years. Six patients (4.2% of the hospital survivors) required another operation before they were 3 years old. Severe arm ischemia occurred after a Blalock-Taussig shunt in 1 infant with Down's syndrome.