Traditional teacher professional development uses a transmission model, in which perceived experts share information with teachers that they are then expected to use in their work with students. In contrast, collaborative inquiry (CI) invites teachers to work with others to answer questions about their work and how they can improve. Lucinda Pease-Alvarez and Katharine Davies Samway describe what they have learned from engaging in CI projects with teachers. They found that successful CI projects focus on what is actually happening, explore real dilemmas and questions, offer flexibility in teachers' and researchers' roles, have institutional support, and include opportunities for teachers to share their work. However, state, district, and school policies as well as teacher working conditions can limit the effectiveness of CI projects.