Abstract:Findings from a longitudinal study of language acquisition in a group of autistic children are presented. Six autistic subjects and six children with Down syndrome, matched on age and MLU at the start of the study, were followed over a period of between 12 and 26 months. Language samples were collected in the children's homes while they interacted with their mothers. Samples of 100 spontaneous child utterances from the transcripts were analyzed using the following measures: MLU, Index of Productive Syntax, lexical diversity, and form class distribution. The results indicate that the majority of these autistic children followed the same general developmental path as the Down syndrome children in this study, and normal children reported in the literature, in the acquisition of grammatical and lexical aspects of language, and confirm previous findings suggesting that autism does not involve a fundamental impairment in formal aspects of language.