This thesis presents two studies examining the relationship between the genre of picture books read to children by their teachers (fictional storybooks or nonfiction information books) and preschoolers' vocabulary and pretend-reading skills. Teachers were randomly assigned to one of three conditions: (1) Read Aloud classrooms in which teachers used information and storybook read-alouds (2) Read Aloud Plus classrooms in which teachers used the read-alouds as well as extension activities, and (3) Control classrooms. Teachers in 26 classrooms and their 278 students participated in this 12-week program. Study 1 investigated whether children learned vocabulary introduced and instructed in information books and storybooks at a similar rate. Results suggest that when vocabulary instruction is embedded in read-alouds and extension activities, the genre of the book in which the word is introduced does not matter. However, if the child's only exposure to the word is during read-alouds, children learn slightly more words from storybooks than information books, on average. Study 2 used a sub-sample of 10 children from the control condition and 10 children whose teachers were faithful to the Read Aloud program. This study explored whether children demonstrate an emergent understanding of genre in their pretend-readings of information books and storybooks. Results suggest many children used emergent informational language in their pretend-readings of information books, but none used this language in their pretend-readings of storybooks. In addition, English language learners who participated in the Read Aloud Program were similar, on average, in their use of emergent informational language to their monolingual peers in the Read Aloud Program, when controlling for initial use of this type of language. However, English language learners who did not participate in the Read Aloud Program were had lower use of emergent informational language, on average, than their monolingual peers in the control condition, controlling for their initial use of this type of language. These studies suggest that information book read-alouds can support children's language and emergent literacy development and that these read-alouds may be especially important for English language learners' emergent literacy development. (author abstract)