To study ED50 and ED90 induction doses of propofol in children.Seventy-two children from 1 to 110 months of age and premedicated with pentobarbital 4 mg/kg participated in the study. Seven different doses of propofol (1.5, 2, 2.5, 3, 3.5, 4 and 4.5 mg/kg) were injected into the dorsal hand or foot vein in 30 seconds. We measured the response to application of the mask, corneal reflex and response to trapezius muscle compression 30 and 60 s after administration. A log-probit statistical analysis was used and complications were noted.The doses that produced 50% elimination of reflexes (ED50) or 90% elimination (ED90) in our patients were 1.74 and 3.95 mg/kg for response to mask; 2.47 and 4.26 mg/kg for elimination of corneal reflex; and 3.27 and 4.79 mg/kg for compression of trapezius. Frequency of pain upon injection was 74% and that of spontaneous movement was 12%. Apnea (breathing halted for longer than 20 s) occurred in 7% of our patients. We recorded no cases of broncho or laryngeal spasm, or skin rash.Induction with propofol is appropriate given the rarity of stimulant effects, but there is a high frequency of pain upon injection, limiting the usefulness of this drug for anesthetic induction in pediatrics. ED50 and ED90 varies depending on the stimulus assessed.