To summarise then, in 1962 RET displayed important features still current. These include the inter-relatedness of cognitive, emotive and behavioural processes, the important role that cognition plays in psychological problems, its humanistic view of the self, and the futility and dangers of self-rating. The emphasis on perpetuation rather than acquisition processes of emotional disturbance holds good now as it did then, and the core view of therapeutic change is essentially the same now as it was in 1962, despite further, more recent elaborations.

Significant change has occurred in RET since 1962 that updates several of Ellis' original ideas. These include the distinction between interpretations (or inferences) and evaluations, the primary of musts in accounting for psychological disturbance, the clear distinction between healthy and unhealthy negative emotions and the greater role according to force and energy in the change process. In addition, a greater emphasis is placed on biological aspects of emotional disturbance now than 30 years ago. Finally, a greater range of cognitive, imaginal, emotive and behavioural methods are found in current RET literature than in Reason and Emotion in Psychotherapy, where Ellis restricts himself to illustrating a few cognitive and behavioural techniques.

RET, then, has grown and developed over the past 30 years. In large part, this reflects the theory's flexibility and the competent people who have worked to make RET one of the most viable and widely used cognitive-behaviour therapies.