Some progress has occurred for the application of assessment procedures for combined disorders. However, far less progress has occurred in the understanding of the natural history and outcome of combined disorders. In addition, relatively little research has been conducted regarding treatment strategies for people with dual disorders, including polydrug abuse and polydrug dependence. As a result, appropriate multidisciplinary and multispecialty service developments, training, and research have not been a focus. Approaches to service provision for persons with dual diagnosis include informal liaison between a drug treatment unit and general psychiatry on an informal basis, formal liaison through defined channels of communication with particular teams, and a specialized unit for treating combined disorders. Personnel training is crucial to recognition of the problem and effective intervention. Administrators and service providers need to be aware of the scale and nature of the problem so that they target resources appropriately. 165 references (Author abstract modified)