Results from a longitudinal study on factors influencing conscience development contributed to our appreciation of the importance of moral internalization for a child's well-being. In this article we first present a summary of the research on moral development in children, including findings from infant research, with emphasis on the work of Robert N. Emde. Characteristics of classical psychoanalytic theory about superego development are compared with more recent insights. This is followed by a short description of two cheating games-as a measure of conscience development-played with 101 preschoolers. Some contrasts in our empirical data between the fair-play group and the children that cheated are presented and discussed in the light of the theoretical points of view. Finally some reflections on future research and the implications for parenting, prevention and clinical work are followed by suggestions for psychoanalytic theory.