How do we determine the effects and effectiveness of activities designed to enhance the professional knowledge and skills of educators so that they might improve the learning of students? Thomas R. Guskey explores the processes and procedures involved in evaluating professional development, from the very simple to the very complex, at five increasing levels of sophistication: Participants’ reactions to professional development How much participants learn Evaluating organizational support and change How participants use their new knowledge and skills Improvement in student learning . . . complete with sample evaluation forms, checklists, and helpful hints and tips.