The information we do know about assistant teachers is presented in this report, including the type of certification, qualifications, and/or other credentials states require for assistant teachers prior to being employed in a state-funded preschool program. We present a summary of the state requirements and variations based on settings, focusing on the most common requirement: the Child Development Associate (CDA) credential and its equivalent. We then review the various pathways and ongoing professional development states have established to support assistant teachers, highlighting a few innovative models. Finally, we discuss the inequitable ways assistant teachers are treated, despite the important role they play in the preschool classroom. (author abstract)