Four hours after acute ingestion of 400 to 1,200 mg of propranolol by a healthy, 3-year-old boy, his plasma concentration of propranolol was 2,289 ng/ml. The only pharmacologic effect observed was a diminished heart rate response to crying and activity. In a second case, a 4-year-old boy on chronic propranolol therapy for renovascular hypertension had a hypoglycemic seizure when solid food was refused for three days because of an oral wound. The hypoglycemia was easily managed with intravenous glucose, and there were no sequelae. The first case alludes to the safety of propranolol in a healthy child even with very high plasma concentrations. The second case suggests the necessity of anticipating and avoiding hypoglycemia that can develop in children on chronic propranolol therapy when caloric intake is impaired.