Infants, children, and adolescents presenting with pain differ dramatically in physical, cognitive, emotional, behavioral, and social characteristics. This chapter presents an overview of basic concepts that should be understood in the delivery of developmentally appropriate care and addresses their relevance to pain assessment and management. The developmental issues concern variations in maturation and growth in perception and central processing of nociceptive information, and its expression in the actions of the child, as well as consideration of how pain affects different spheres of activity at different ages.