This book is a step-by-step guide for correctly applying Fishbein and Ajzen's theories which together form " . . the dominant conceptual framework for predicting, explaining, and changing human social behavior" (Ajzen, 2012). Evaluators and educational researchers, however, have often made less than optimal use of the theory of reasoned action, and the later theory of planned behavior,to understand, measure, and influence beliefs, attitudes, and behavior. This book is written expressly for investigators who are not trained in attitude theory and measurement. It provides examples from the fields of evaluation and educational research at each step, including many from the author's applications. This book offers clear conceptual and operational definitions of belief, attitude, behavior, and other variables that are components of the theories. Figures illustrate relations among the variables. One chapter critically reviews efforts to apply the theories in evaluation and educational research, using positive and negative examples. The author has 30 years' experience in evaluation and research, a doctorate in education, and training in attitude theory and measurement with Martin Fishbein. The author's dissertation study was the first successful application of the theory of reasoned action to the issue of participation in adult education, and prompted others in that field to apply the theory.