Propranolol hydrochloride is a safe and effective medication for treating infantile hemangiomas (IHs), with decreases in IH volume, color, and elevation. Forty children between the ages of 9 weeks and 5 years with facial IHs or IHs in sites with the potential for disfigurement were randomly assigned to receive propranolol or placebo oral solution 2 mg/kg per day divided 3 times daily for 6 months. Baseline electrocardiogram, echocardiogram, and laboratory evaluations were performed. Monitoring of heart rate, blood pressure, and blood glucose was performed at each visit. Children younger than 6 months were admitted to the hospital for monitoring after their first dose at weeks 1 and 2. Efficacy was assessed by performing blinded volume measurements at weeks 0, 4, 8, 12, 16, 20, and 24 and blinded investigator scoring of photographs at weeks 0, 12, and 24. IH growth stopped by week 4 in the propranolol group. Significant differences in the percent change in volume were seen between groups, with the largest difference at week 12. Significant decrease in IH redness and elevation occurred in the propranolol group at weeks 12 and 24 (P = .01 and .001, respectively). No significant hypoglycemia, hypotension, or bradycardia occurred. One child discontinued the study because of an upper respiratory tract infection. Other adverse events included bronchiolitis, gastroenteritis, streptococcal infection, cool extremities, dental caries, and sleep disturbance. Propranolol hydrochloride administered orally at 2 mg/kg per day reduced the volume, color, and elevation of focal and segmental IH in infants younger than 6 months and children up to 5 years of age.