Numerous arguments have addressed the controversies surrounding the category of emotional disturbance (ED) and the exclusion, or proposed inclusion, of students with social maladjustment (SM). In this article we address the consensually agreed upon characteristics of ED that are in common with SM, in addition to examining characteristics that supposedly also differentiate students who are ED from those who are SM. Given that SM has not been clearly defined and therefore it has proven to be an exceedingly difficult task for practitioners to differentiate children who are ED from SM suggests that they should be considered as a single condition termed ED/SM. Characteristics of ED and SM have substantial overlap, but apparently enough difference is noted to argue that they are distinguishable disorders requiring differential diagnoses and treatment, resulting in one that warrants special education services, and one that does not. We argue that whether these children are classified as ED, SM, or ED/SM, they all should qualify for special education services based primarily on the inescapable fact that they need professional assistance if their condition militates against optimal educational attainment. Furthermore, there exists little, if any, differentiation of effective and enduring treatment on the basis of whether a child is classified as either ED or SM. Finally, an alternative nonenvironmental explanation is offered for the apparent increase in incidence of characteristics associated with ED/SM. The alternative explanation is based on the genetic phenomenon heterosis that provides a plausible argument that secular changes in several cognitive, physical, and psychological characteristics may have the same nonenvironmental etiology. © 2004 Wiley Periodicals, Inc. Psychol Schs 41: 861–865, 2004.