We have reviewed the records of 65 children with paroxysmal supraventricular tachycardia (PST) without congenital heart disease followed a mean of 4 years, with a total of 121 episodes. PST appeared before 6 months of age in 42 (64.6%) children. Thirteen patients (20%) had a present factor which might predispose to PST in 66.2% of the patients who were younger than 6 months of age, and in only 4.3% of those over 6 months. Wolff-Parkinson-White syndrome was present on surface ECG during sinus rhythm in 26.1% of children younger than 6 months, and in 39.1% of those over 6 months. Digoxin was the initial treatment in 84.3% of the episodes with a success rate of 75% when were employed alone and of 84.2% when were employed in combination of quinidine. PST recurred at least once in 35 children (53.8%), the 90% within three months of the first episode. All patients were alive and 63 (96.9%) doing well. One patient developed cerebral anoxia and now has hemiparesia and another patient has incessant PST. We conclude that children with PST without congenital heart disease and without delay in diagnosis had a good outcome.