This study examined young children's spontaneous participation during classroom book reading in response to different types of books. Twenty kindergarten teachers read four books--two fiction (familiar/unfamiliar story format) and two information books (expository/narrative text). The majority of children's spontaneous participation was related to the book illustrations and the children's personal experiences. Information books elicited more comments about personal experiences, while fiction books elicited more predictions, personal responses, chiming, recall, clarifying, and evaluation comments. The minimal expository text prompted more personal experiences and analytical comments compared to the narrative text of the information book. The familiar story form provoked more predictive and analytical comments. Finally, the quality of illustrations instigated an increased proportion of children's labeling comments.