We examined the effect of a modified dialogic reading intervention on levels of verbal participation and vocabulary growth in nine preschool children with autism spectrum disorder (ASD) using single-case design methodology. Baseline book reading resulted in consistently low levels of verbal participation followed by an immediate increase in verbal participation during dialogic book reading sessions for all children. Dialogic reading also resulted in greater gains in book-specific vocabulary for all children, as compared with baseline book reading sessions. The improvement in verbal participation was characterized by more frequent responses to the adults' question prompts during reading. No improvements in children's independent initiations of comments or questions during the book reading activity were observed. (author abstract)