This technical assistance paper provides preschool planners and staff with information on developmental characteristics of preschool children relevant to planning and providing a quality preschool program. Following a case scenario underscoring the need for understanding child development, a theoretical framework concerning child development is presented. The framework includes summaries of the work of theorists and provides explanations about significant aspects of social, emotional, physical, and cognitive development. Significant developmental principles are discussed, and the normative development characteristics for 3-, 4-, and 5-year-old children are presented in the form of charts. The paper also examines the importance of understanding individual differences, and the teacher's responsibilities toward each child. Concluding comments are on the valuable role of play, and the influences of family, culture, and community on the development of the child. Contains 18 references. (BAC)