Grammar is frequently considered to be a strength in the cognitive profile of individuals with autism spectrum disorders (ASDs); however, few studies have investigated how abstract (i.e. distinct from specific lexical items) is the grammatical knowledge of individuals with ASD. In this study, we examine the extent to which children with ASD have abstracted the transitive (SVO) frame in English. Participants in a longitudinal study of language acquisition in children with autism (17 children with ASD averaging 41 months of age, 18 TD children averaging 28 months of age) were taught two novel verbs in transitive sentences and asked (via intermodal preferential looking) whether these verbs mapped onto novel causative vs. noncausative actions. Both groups consistently mapped the verbs onto the causative actions (i.e. they engaged in syntactic bootstrapping). Moreover, the children with ASD's performance on this task was significantly and independently predicted by both vocabulary and sentence-processing measures obtained 8 months earlier. We conclude that many children with ASD are able to generalize grammatical patterns, and this ability may derive from earlier lexical and grammatical knowledge. Autism Res2011,4:422–437. © 2011 International Society for Autism Research, Wiley Periodicals, Inc.