Shared reading is reported to be the single best instructional practice for emergent literacy skills. Vocabulary instruction practices implemented during shared reading by both Head Start (HS) teachers and teachers from more affluent private school settings were compared to determine whether there were differences between the 2 groups of teachers in their implementation of research-based practices. HS teachers implemented vocabulary instruction practices during shared reading more often, and chose different words to instruct, than private school teachers. Whereas 78% of HS teachers provided some vocabulary instruction during shared reading, only 59% of private school teachers did so. Among those teachers who provided vocabulary instruction during shared reading, HS teachers used significantly more contextualization strategies for word instruction than private school teachers. These findings suggest that preschool teachers who work with children from high-needs backgrounds use vocabulary instruction during shared reading as a way to bolster children's vocabularies more frequently than teachers working in private preschools that serve children from more privileged backgrounds. Extratextual language was also compared, and private school teachers had a higher mean length of utterance and type-token ratio than the HS teachers. Practice or Policy: Professional development is recommended for preschool teachers to increase the implementation of best practices for vocabulary instruction during shared reading. (author abstract)