In the Assessing Preschool Professionals' Learning Experiences (APPLE) project, we partnered with ecQ-net and the Ohio Department of Education to conduct an independent evaluation of Ohio's state-sponsored language and literacy professional development for early childhood educators. Participating educators were randomly assigned to experience the state's 30-hour language and literacy professional development course, the course plus ongoing in-class coaching, or professional development on an alternative topic. Largely, the language and literacy professional development did not improve educators' knowledge, dispositions, or classroom practices, nor did it improve children's language and literacy outcomes. This may have been due to variability in implementation. Although the professional development was rated favorably, course sessions varied in the extent to which key components were implemented and educators received widely differing amounts of coaching. Overall, results caution against investing in large-scale professional development without evidence that such efforts yield intended benefits for educators and children. (author abstract)