In the review of thousands of psychiatric reports submitted in connection with applications for disability benefits under the social security law, it was found that many of these reports did not consider the concept of regression in evaluating the impact of the psychiatric illness. Our experience with physiological regression is illustrated by two cases which emphasize the concept that loss of function for an extended period of time should be associated with concomitant evidence of physiological regression. This furnishes a reasonable basis for the conclusion that the psychiatric impairment has resulted in a substantial and persistent loss of functional capacity.