In the United States, research directed specifically at improving our understanding of the psychiatric assessment and treatment of individuals with intellectual disabilities (ID) has grown, yet lags far behind efforts for typically developing children and adults. In the United States, a lack of a national approach to the mental health problems of people with ID has likely contributed to a lack of a clear and cohesive national research agenda for "dual diagnosis" of intellectual disabilities and mental health disorders. Despite these concerns, much has been learned and important progress has been made. This article provides an overview of the latest developments in research and social policy on behalf of persons with ID and mental health needs in the United States.