In a recent article in this journal Gresham and Gansle (1992a) argued that the Diagnostic and Statistical Manual of Mental Disorders (3rd edition, DSM-III-R) (APA, 1987) is irrelevant for the practice of school psychology based on five misguided assumptions including, 1) a medical model conceptualization of behavior, 2) reliability, 3) validity, 4) relevancy for special education placement, and, 5) treatment validity. It was argued that the absence of treatment validity is the most serious issue among the problems with the DSM-III-R. After providing an overview of these misguided assumptions, the authors advanced a functional analysis of behavior as being more relevant to various dimensions of school psychological practice (e.g., assessment, classification, placement, and intervention).A number of issues were raised in response to Gresham and Gansle (e.g., Hynd, 1992;Martens, 1992;Reynolds, 1992). Although many issues were addressed in the series of papers and in the rejoinder (Gresham & Gansle, 1992b), a number of fundamental assumptions pertaining to the alternatives proposed by Gresham and Gansle remain to be elucidated. Specifically, the purpose of our paper is to elaborate on several issues surrounding the treatment validity construct and a functional analysis of behavior. Embedded within this discussion are some empirical directions that will need to be addressed in the future.The lack of treatment validity associated with DSM-III-R is the first issue in need of clarification. Treatment validity is a relatively recent "measurement" construct first introduced into the behavioral literature (e.g., Nelson & Hayes, Requests for reprints should be sent to