The induction dose of propofol in infants 1-6 months of age and in children 10-16 years of age. The propofol dose needed for satisfactory induction of anesthesia was determined in 22 infants 1-6 months of age and 22 children 10-16 yr of age. A single bolus of propofol was given over 10 s. Thirty seconds after injection the lid reflex was tested and the anesthesia mask was applied. The patient was considered to be asleep if there were no gross movements during the next 30 s while the patient breathed O2. The dose required for satisfactory induction in 50% of patients (ED50) (+/- SE) was 3.0 +/- 0.2 mg/kg in infants and 2.4 +/- 0.1 mg/kg in older children (P less than 0.02). Pain on injection occurred in 50% of the infants and 18% of the children. 