An evidence-based approach to professional development is described on the basis of the findings from a series of research syntheses and meta-analyses of adult learning methods and strategies. The approach, called PALS (Participatory Adult Learning Strategy), places major emphasis on both active learner involvement in all aspects of training opportunities and instructor/trainer-guided learner experiences. The use of PALS practices has been found to be associated with improved learner knowledge, use, and mastery of different types of intervention practices. Implications for in-service training are described. (Contains 3 figures and 3 tables.)