Never before in the history of the teaching profession has there been such a need for comprehensive evaluation of all teacher preparation programs, most especially professional development schools (PDSs). This need is driven not only by the pressures of the age of accountability, but also by the need for the PDS movement to act ethically and responsibly. All PDS programs, regardless of size and scope, should undertake ongoing, meaningful examinations of their effectiveness. Program evaluation is not an afterthought, but a deliberate ongoing inquiry that serves to strengthen the PDS effort. This chapter reviews many options and approaches that could be used to guide such inquiry. The purpose of the chapter is to serve program evaluators and stakeholders as they formulate an approach to assessing the effectiveness of their PDS program. (Contains 1 table and 1 note.)