This survey of the instruments and methods that are currently available for assessing mental health problems in persons with mental retardation lists formalized instruments and interview techniques and evaluates them from a methodological perspective. Emphasis is on the assessment and classification of disorders rather than on the evaluation of adaptive behaviors or treatment effects. Information was solicited from several professional organizations with an interest in behavior, psychopathology, and developmental disabilities through letters sent to 50 prominent researchers and through computer searches of the literature. Approximately 40 relevant instruments were identified. These are described in three sections: (1) the more established instruments, most of which have been published, with detailed descriptions and thorough critiques; (2) relatively new or unpublished instruments, with brief summaries and critiques; and (3) relevant instruments considered peripheral to assessment of behavior disorders, with brief descriptions and no appraisal of psychometric characteristics. Eight tables summarize information about the instruments. Three appendices provide supplemental information about the survey process and the instruments reviewed. (SLD)