Pain is subjective. The pain response is individual and is learned through social learning and experience. Early pain experiences may play a particularly important role in shaping an individual's pain responses. Painful medical procedures such as immunizations, venipunctures and dental care, and minor emergency department procedures such as laceration repair, compose a significant portion of the average child's experience with painful events. Inadequate relief of pain and distress during childhood painful medical procedures may have long-term negative effects on future pain tolerance and pain responses. This article reviews the evidence for long-term negative effects of inadequately treated procedural pain, the determinants of an individual's pain response, tools to assess pain in children, and interventions to reduce procedural pain and distress. Future research directions and a model for conceptualizing and studying pediatric procedural pain are proposed.