There is growing evidence that children have short- and long-term physical, physiological, and psychological effects due to untreated acute pain. Because the majority of children who seek care in an emergency department present with pain or experience pain during the evaluation and treatment in the emergency department, optimal assessment and treatment of pain are paramount for this population. This review will highlight the many complexities of the assessment of pain for the pediatric patient. In addition, a variety of factors that affect the self-report of pain in children will be identified. Optimizing the utility of a pain assessment remains a challenge for the health care provider in the emergency setting. The common goal of a decreased experience of pain for children through improved analgesic administration remains.