Research in developmental psychology has almost invariably neglected to distinguish between categorization of the self in group terms and subjective identification with a group. Methodologically, this has been exemplified in investigators’ widespread assumption that children's ascription of group labels (e.g., ‘I'm a Chinese American’) reflects proper identification with the named category. We argue that more subtle measures are required in order to determine whether social groups have become assimilated to the self-concept, as would be required in order to infer that identification (rather than mere categorization) has taken place. Following a review of extant literature, we introduce our own program of research, conducted over the last decade, which draws upon methods from cognitive social psychology. Based on this research, we conclude that genuine identification with social groups is likely to be in place at least by the age of five years. However, our findings suggest that cognitive aspects of identification are likely to antecede affective aspects.