The aim of the study reported here was to establish whether the behavioural profiles of children with high-functioning autism (HFA) come to approximate the profile of children with Asperger Syndrome (AS) over time. The parents of 21 children with HFA and 19 children with AS, all aged between five and 11 years and matched on chronological and mental age, were interviewed using the Autism Behaviour Checklist. The parents reported on their child's current behavioural presentation as well as on their early (childhood) behaviours. The hypothesis that the children with HFA would show more severe symptomatology in comparison to the children with AS on their early behavioural scores was supported. Moreover, the two groups were indistinguishable on their current behavioural profiles, providing support for Szatmari's (2000a; 2000b) developmental model of autism and AS. The lack of qualitative differences in the behavioural profiles between the two groups during early and middle childhood was taken as evidence that AS is a milder variant of autism. (Contains 4 figures and 5 tables.)