While the literature on treatment of dually diagnosed individuals continues to grow, few studies have examined the potential interactions between behavioral interventions and pharmacological interventions in treating persons with a developmental disability and a concurrent psychiatric disorder. The current theoretical paper discusses different manners in which psychotropic medications and behavioral interventions can interact, including the potential for facilitative or inhibitory effects of one treatment modality on the other. Possible permutations of these interactions are discussed. Case examples, including objective measures of psychiatric and behavioral symptoms over time, representing possible illustrations of these permutations, are presented. The authors argue that in many cases the potential effect of one treatment procedure on the efficacy of another may be an important consideration in treating dually diagnosed individuals.