Weight gain is an often-observed side effect of atypical antipsychotics (AAPs) and is particularly significant in individuals with intellectual disabilities (ID). The majority of individuals treated with AAPs will gain at least 10% of their initial body weight over the course of therapy (Umbricht & Kane, 1996). One's genetic constitution is an important factor that influences the variability of weight gain observed among patients taking AAPs. This article reviews the existing literature on psychopharmacogenetics of AAP-induced weight gain and the importance of this research for individuals with ID. (Contains 2 tables.)