Research Findings: This study examined how teacher--child conversations unfold during shared book reading in Head Start classrooms as well as the relations between that talk and children's vocabulary learning. Book reading experiences in 27 Head Start classrooms were videotaped and coded for teacher talk, child responses, teacher follow-up remarks, and teacher wait time; we also assessed children's vocabulary learning. Findings indicated that Head Start teachers infrequently asked open prompts or provided book-related comments; the predominant tool used in shared reading was the closed prompt. Teachers generally accepted 1 answer per question, and children's answers were nearly always correct. Wait time was rarely observed. Across the sample, more child talk was predictive of stronger child vocabulary learning. For children with low initial vocabulary skills, learning was also linked to more expository comments by teachers. Practice or Policy: Findings help to map out the sequence of instructional events that make up preschool classroom conversations and provide insight into potential levers for improvement.