A review of Piaget's theory and research on children's cognitive development is presented, including a discussion of the psychological structures of intelligence, developmental constructivism, and the evolution of knowledge as a subject-object relation. Piaget's assessment techniques are summarized, including moral development, number conservation, spatial operations, and a comparison between intelligence quotient and Piaget's assessment of intelligence. Implications of Piaget's theory for educational practice are discussed in terms of the need for research, recommendations for teacher education, educational objectives, and teaching methods. A guide to conducting Piagetian child assessments and a six-item annotated bibliography on Piagetian theory and testing are appended. A 50-item unannotated bibliography is also included. (MH)