This study describes an evaluation of a read aloud intervention to improve comprehension and vocabulary of first-grade students. Twelve teachers were randomly assigned to an intervention or comparison condition. The study lasted 19 weeks, and the intervention focused on the systematic use of narrative and expository texts and dialogic interactions between teachers and students delivered in whole-classroom formats. Read aloud intervention lessons included before-, during-, and after-reading components and explicit instruction targeted comprehension and vocabulary knowledge. Teachers in the comparison condition implemented the same amount of read aloud instruction, focusing on strategies they believed would help their students with comprehension and vocabulary. On some, but not all, outcome measures, intervention students at low risk and high risk for language difficulties outperformed comparable students in the comparison group. Implications are discussed. (Contains 1 note and 7 tables.)