This study examined the relationship between self-injurious behavior and caloric intake. Behavioral, dietary, and weight/height indices obtained on 80 neurodevelopmentally disabled and autistic clients revealed that maintenance on high caloric diets significantly predicted the occurrence of self-injurious behavior in male clients. Male clients with self-injurious behavior were also outside their recommended weight to height index. Systematic studies are needed to assess the relationship among diet, the endogenous opioid system, and self-injurious behavior. © 1992 Plenum Publishing Corporation.