The engagement of teachers as raters to score constructed response items on assessments of student learning is widely claimed to be a valuable vehicle for professional development. This paper examines the evidence behind those claims from several sources, including research and reports over the past two decades, information from a dozen state educational agencies regarding past and ongoing involvement of teachers in scoring-related activities as of 2001, and interviews with educators who served a decade or more ago for one state's innovative performance assessment program. That evidence reveals that the impact of scoring experience on teachers is more provisional and nuanced than has been suggested. The author identifies possible issues and implications associated with attempts to distill meaningful skills and knowledge from hand-scoring training and practice, along with other forms of teacher involvement in assessment development and implementation. The paper concludes with a series of research questions that—based on current and proposed practice for the coming decade—seem to the author to require the most immediate attention.