In this retrospective on behavior therapy on the occasion of ABCT’s 50th anniversary, I describe my role in several developments that I believe have been important for the field. First, behavior therapy has moved from advancing a predetermined set of theories and techniques (“the conditioning therapies”) to a more general and stronger focus on studying the most scientifically sound and useful conceptions of psychopathology, assessment, and intervention, with less emphasis on preconceived ideas about where the best answers would lie. In other words, I have tried throughout my career to promote a conceptualization of behavior therapy in terms more of an epistemology than an accepted corpus of techniques, theories, and data. Next, I review the brouhaha about behavior therapy during the U.S. Senate hearings in the mid-1970s on extreme behavior control measures at the federal prison in Springfield, MO, where reasonable, important, but misdirected criticisms were being made against measures such as ECT and lobotomy in the name of behavior therapy. Next I review the formal introduction of cognitive factors into the mainstream of behavior therapy, leading to a broader and more sophisticated conceptualization that came to be known as cognitive behavior therapy. These developments have begun to bring our scientific study of the human condition more in line with contemporary theory and research in cognitive psychology and have expanded the applicability and effectiveness of our science-based assessment and intervention. Next, I discuss the intricate and mutually enriching interplay between science and application, with special attention to the underappreciated role of clinical observation and innovation in setting a worthwhile scientific agenda for understanding and alleviating human distress and enhancing human potential. Further, I explore the sometimes controversial effort to look to nonbehavioral theory, data, and clinical observations for ideas to enhance our effectiveness as clinicians. Clinically nuanced and hard-headed analysis of psychological problems need not be inconsistent with a consideration of other paradigms such as the many variants of psychoanalysis and humanistic-existential theories. Finally I recount the events surrounding my 1974 AABT presidential address, in which I argued on ethical and political grounds against sexual reorientation treatment for homosexuality. My original argument has been expanded to the proposition that clinical assessment is inherently constructive and that therapy goals are determined primarily by clinicians in a manner that reflects both their theoretical and moral biases.