My aim in this paper is to consider what it means to engage and communicate with another person. I do so by adopting the approach of developmental psychopathology, and compare and contrast the structure of communication that is manifest by typically developing infants on the one hand, and by children and adolescents with autism on the other. I highlight the pivotal significance of human beings' propensity to share or otherwise co-ordinate experiences with others, and analyze the conditions that make sharing and other forms of intersubjective relatedness possible. Often, discussions that oppose cognitive, affective, and motivational accounts of autism are pursued in an inappropriate frame of reference: at root, we need to understand the nature and developmental implications of affected children's difficulties in achieving communicative depth. In the pursuit of such understanding, we may gain insights into typically developing infants' capacities for intersubjective engagement.