Traditional systems of teacher evaluation are often ineffective because they rely on outmoded evaluative criteria, usually in the form of checklists; simplistic assessments, such as "needs improvement"; procedures that fail to differentiate between new and veteran teachers' experience and expertise; lack of consistency among evaluators; and one-way, top-down communication. Noted educator Charlotte Danielson suggests that we can remedy these characteristics by ensuring that teacher evaluation satisfies two important goals--that it assures teacher quality and promotes professional development. A two-year pilot program in Chicago Public Schools, which used Danielson's Framework for Teaching to measure teachers' classroom performance, has documented the benefits of this approach. Administrators and teachers noted that the framework provided a consistent definition of good teaching, opportunities to engage in meaningful conversations about practice, and a focus on what really matters in good teaching. This article addresses the topics of staff assessment, teacher supervision, and professional development. (Contains 1 figure and 1 endnote.)