Childhood amnesia refers to the inability of children and adults to recall events that took place during their infancy and early childhood. Freud originally coined the term on the basis of clinical interviews; subsequent empirical investigations have confirmed many of Freud's original observations, but not his explanation for the phenomenon. Consistent with Freud's view, childhood amnesia is not a unitary phenomenon, but rather consists of at least two separate phases. In this article, we review the evidence for a two-stage phenomenon and highlight some of the major developmental changes that might contribute to each phase. We reject Freud's repression explanation and argue instead that a comprehensive theory of childhood amnesia will require an understanding of neurological, cognitive, language, and social development. WIREs Cogni Sci 2011 2 136-145 DOI: 10.1002/wcs.107 For further resources related to this article, please visit the WIREs website.