This article traces the development of process and outcome research from before the foundation of counseling psychology in 1946 to the present time. First, theoretical contributions are focused on, with particular attention to the influence of Carl Rogers's theory, behavior theory, psychoanalytic theory, systems theory, interpersonal theory, and social influence theory. Next, Eysenck's challenge to the efficacy of psychotherapy; the uniformity myth that process and outcome are similar across diverse clients, therapists, and contexts; and changes in research methods over the years are covered. The article concludes with recommendations for future research.Interest in examining the helping process has existed for a long time, predating the inception of counseling psychology. Healers all over the world have tried to understand whether what they are doing is helpful and whether what they do leads to change. Early psychotherapists wrote extensively about how to do therapy. For example, Sigmund Freud amassed observations of psychoanalysis, which he used to develop his theories of therapeutic change. Eschewing conventional experimental methods, Freud did not quantify his observations (Schultz, 1972) and thus was not considered scientific. Use of the scientific method to investigate the helping process did not begin in earnest until the middle of the 20th century, thus coinciding with the founding of counseling psychology as a discipline.The purpose of this article is to review the development of research on the process and outcome of counseling and psychotherapy to the present day and to interpret the factors that shaped the field into its current state. Our primary focus is on process research, but we include issues in outcome research that have had an impact on process research. We emphasize individual rather than group or family therapy research. Historical events are not considered in exact chronological order but rather in the rough order of our perceptions of their impact on the field of counseling psychology.