Extension and evaluation share some similar challenges, including working with diverse stakeholders, parallel processes for focusing priorities, meeting common standards of excellence, and adapting to globalization, new technologies, and changing times. Evaluations of extension programs have helped clarify how change occurs, especially the relationship between knowledge change and behavior change, the importance of systems thinking, the purposes of evaluation (accountability versus improvement versus knowledge generation), the significance of process use, and the challenge of matching methods to evaluation questions, resources, and purposes to ensure methodological appropriateness. (Contains 4 tables.)