School psychologists need to assess the severity of behavior disorders accurately to facilitate comprehensive diagnosis, to provide appropriate intervention, to enlighten research efforts, and to be in compliance with state and federal guidelines. Although clinicians in fields such as mental retardation categorize severity of behavior to make diagnostic and general treatment decisions, school psychologists rarely attempt to assess severity in any systematic or comprehensive way. The primary purpose of this study is to see how 92 practicing school psychologists rank 11 variables in their assessments of SED in school-age children. A secondary purpose is to examine the extent of school psychologists' reliance upon clinical and empirical criteria in assessing the seventy of SED. It is concluded that school psychologists agree in their rankings of variables from most to least important and that they do not consider empirical criteria more important than clinically based criteria when assessing SED. Implications for practice are presented.The accurate assessment of the severity of behavior disorders by school psychologists is necessary to facilitate comprehensive diagnosis, to provide appropriate intervention, to enlighten research efforts, and to be in compliance with state and federal guidelines. Children who exhibit more severe behavior often need additional or more intensive services. Epstein, Detwiler, and Reitz (1985) pointed out that higher quality interventions will not be forthcoming until the behaviors of children now classified as seriously emotionally disturbed (SED) or behavior disordered (BD) are more accurately assessed. Assessing the severity of behavior is also necessary to satisfy the least restrictive environment (LRE) and appropriate education requirements of the Individuals with Disabilities Education Act (IDEA, 1990). School psychologists cannot recommend appropriate placements and treatment plans for children with SED until an accurate measure of severity is obtained. Unfortunately, there is little systematic mention of assessing for severity of behavior disorders in texts on child psychopathology (Achenbach,