This article is a sketch of the historical development of the field of behavioral and non-behavioral therapy research. Four phases are characterized: (1) establishing scientific research (1927-1954), (2) searching for scientific rigor (1955-1969), (3) expansion and organization (1970-1983), and (4) consolidation and reformulation (1984 present). Continuities between and key developments within successive phases are outlined, with emphasis given to methodological innovations. The corroboration of select findings about process and outcome and the development of several critical discourses within the third and fourth phases have implications for the provision of mental health care and for policy discussions.