Preschoolers' vocabulary development is integral to their oral language development, which is critical for literacy learning. Accordingly, Early Reading First (ERF) programs provide specific professional development intended to strengthen preschool teachers' vocabulary instruction. In 2006, as project directors, we implemented a professional development plan intended to produce stronger methods for teaching vocabulary. Throughout that year, we observed notable changes in teachers' instruction, which led to an acceleration of children's vocabulary growth. (author abstract)