Researchers and clinicians now recognize that adults with intellectual disabilities (ID) evince the full range of mental health concerns. Only recently, however, have attempts been made to develop evidence-based diagnostic and screening methods to identify these problems. Given that the way these people display symptoms of psychopathology may depart from symptom presentation in the general population, tests of this sort are essential both to enhance the reliability and validity of diagnosis as well as to educate professionals on symptom profiles for those people with ID. This article reviews 3 of the better established scales that have been developed primarily for diagnostic purposes and reviews key parameters and issues in scale development and use. The implications of these data for practice and potential future research trends are discussed. (Contains 1 figure.)