Developmentally disabled clients with a concomitant mental illness are often underserved or inappropriately treated because of interorganizational barriers, leading to unnecessary hospitalization and lengthy delays in community placement. To overcome these barriers, agencies responsible for developmental disabilities and mental health services in Spokane County in Washington State developed a collaborative system of care in 1989. An interagency consortium was established to promote coordination of services between the community mental health center, the state hospital, the county human services agency, the state's regional developmental disability service agency, the state institution for the developmentally disabled, and several community agencies serving developmentally disabled persons. Between 1990 and 1992, admissions of developmentally disabled persons to the state hospital were more likely to be appropriate admissions of persons suffering from a mental illness, developmentally disabled clients were discharged more efficiently, and crisis respite services were used in place of hospitalization. In addition, anecdotal reports indicated a reduction of interagency tensions.