The pharmacokinetics and pharmacodynamics of opioid and nonopioid analgesics and adjuvants are discussed in a framework applicable to daily clinical practice. In this paper we elicit the impact of physiology of the developing child on drug dosing and drug choice. Conversely, the pharmacologic effect of various analgesics on the physiologic function of key organ systems is presented as well. This review offers the scientific justification for pain intervention philosophies, and thus broadens the armamentarium of the physician who manages pain in children. Research efforts and clinical findings to date of frequently employed analgesics and adjuvants are discussed.