This chapter summarizes parts of an ongoing research project on the cognitive development of chimpanzee infants, focusing on their social cognition. Since Premack and Woodruff's (1978) article on "theory of mind" in the chimpanzee, studies on social cognition in nonhuman primates from comparative and developmental perspectives have attracted considerable attention. The idea of theory of mind, the ability to infer the mental state of a conspecific, has been elaborated by developmental psychologists, and many experimental studies have been conducted with human children using "false belief" tasks. The research described in this chapter deals with the development of various social cognitive abilities in mother-raised chimpanzees. With regard to the development of social cognition, the chapter also focuses on the social transmission of knowledge from mother to infant. It also examines the interrelated abilities of early social cognition with special reference to gaze: recognition of the mother's face, mutual gaze, gaze following, and triadic interactions.