In 1917, social work had only one theoretical and practice model-social casework. 1 In the early 1920s, social casework was joined by another model, psychoanalysis. The 1930s brought two more models, and the next two decades ushered in others. In the 1960s and 1970s, a plethora ofmodels developed, including family systems, behavioral and cognitive, and many others associated with the "human potential movement" (e.g., gestalt, transactional analysis, existential social work). Theoretical and practice models continue to proliferate (e.g., hypnotherapy, feminist therapy, solution-centered therapy, and a number of brief-treatment models). Corsini (1981), for example, has listed 250 different systems of psychotherapy.