The presence or absence of clinically delayed language development prior to 3 years of age is a key, but contentious, clinical feature distinguishing autism from Asperger's disorder. The aim of this study was to examine language processing in children with high-functioning autism (HFA) and Asperger's disorder (AD) using a task which taps lexical processing, a core language ability. Eleven individuals with HFA, 11 with AD and 11 typically developing (TD) individuals completed a masked priming task, a psycholinguistic paradigm that directly examines lexical processes. Within-group analyses revealed the AD and TD groups had intact lexical processing systems and orthographic processing of the written word. The outcomes for the HFA group were ambiguous, suggesting that their lexical processing system is either delayed or is structurally different. This suggests that fundamental differences in lexical processing exist between HFA and AD and remain evident later in development. (Contains 1 note, 2 tables and 1 figure.)