Professional development and teacher education policies have the potential to greatly affect teachers' abilities to teach and, as a result, students' abilities to learn. States can play varied roles in the provision of teacher education and professional development. This policy brief summarizes states' policy approaches to teacher professional development and education throughout teachers' careers. It explores what states are currently doing in the realms of pre-service education, induction and mentoring, ongoing professional development, and teacher evaluation, as well as the existing evidence regarding the effectiveness of such policies. We find that states play disparate roles in the provision of teacher education and professional development that fall along the regulatory spectrum from highly prescriptive to rather laissez-faire. Research on the effects of such policies is still in the early stages, and more attention is needed to determine the effectiveness of states' professional development policies.