In this article, we review Wolpe’s (1954) work demonstrating the relative efficacy of reciprocal inhibition in the treatment of anxiety disorders. Although Wolpe’s article refers to studies involving adults, the findings and implications are equally valid for therapy with children and adolescents. Wolpe’s groundbreaking work as a behaviourist was grounded in his belief that behaviour therapy could be as much an applied science as could any other aspect of medicine. He is best known for his work in the areas of desensitization and assertiveness training, both of which have become important elements of modern behavioural therapy. In his seminal article, Wolpe argued that any fundamental reduction in the levels of anxiety were frequently the result of reciprocal inhibition. According to Wolpe, reciprocal inhibition refers to the complete or partial suppression of anxiety responses as a consequence of the immediate evocation of other responses physiologically antagonistic to anxiety, i.e., the technique seeks to condition a new response that is considered incompatible with the response to be eliminated. Wolpe’s theory of reciprocal inhibition, like a number of other learning-based theories, was based on experiments with animals. Following this experimentation, Wolpe was confident that reciprocal inhibition was effective in interrupting conditioned responses in animals in ways that extinction was not. This finding led Wolpe to develop the hypothesis that if a response incompatible with anxiety can be made to occur in humans in the presence of anxiety-provoking stimuli, then it will weaken the relationship between these stimuli and the anxiety responses. Wolpe’s enduring contribution was in laying the foundations for experimentation in the broad field of individual psychotherapy.