Hobson (Autism and the development of mind. Lawrence Erlbaum, Hove, UK 1993) has proposed that the cognitive and linguistic disabilities that characterise autism result from abnormalities in inter-subjective engagement during infancy, which in turn results in impaired reflective self-awareness. The aim of the present study was to test Hobson's hypothesis by examining self-understanding in Asperger's syndrome (AS) using Damon and Hart's (Self-understanding in childhood and adolescence. Cambridge University Press, Cambridge, 1988) model of self-concept. Ten participants with Asperger's syndrome were compared with ten non AS controls using the Self-understanding Interview (Damon and Hart in Self-understanding in Childhood and Adolescence. Cambridge University Press, Cambridge, 1988). The study found that the Asperger's group demonstrated impairment in the "self-as-object" and "self-as-subject" domains of the Self-understanding Interview, which supported Hobson's concept of an impaired capacity for self-awareness and self-reflection in people with ASD. The results are discussed with reference to previous research regarding the development of self-understanding in people with ASD.