Acetaminophen (paracetamol, APAP) is one of the safest and most widely used analgesic-antipyretics in children. When compared to other analgesic-antipyretics, acetaminophen has been shown in many clinical studies to have equivalent efficacy. Based on available clinical and pharmacokinetic data, acetaminophen should be dosed with single doses in the range of 10-15 mg/kg at 4-hour intervals. However, many dosing schedules recommend inadequate amounts of acetaminophen. Dosing schedules based on weight can be constructed that will accurately keep each dose within the recommended range. Dosing also can be adapted to an age-based schedule, which will provide consistent dosing from infancy to adolescence. The principles used to derive the age-based dosing schedule have potential application for use with other pharmacologic agents, particularly nonprescription drugs.