Over the years, many people have inquired about the validity and reliability of the NSDC Standards for Staff Development self-assessment instrument included at the end of the standards book (NSDC, 2001). My answer to those who asked was that the self-assessment had face validity. Today, I can refer individuals to the Standards Assessment Inventory, which offers a valid and reliable measure of the quality of professional development in a school as defined by NSDC’s Standards for Staff Development. While the original self-assessment is a useful tool for initiating conversation, encouraging reflection, and spurring planning, NSDC leaders became concerned when we learned that many schools were using it for other purposes. We felt compelled to provide an instrument that was more research-based. As a result, we