OBJECTIVE: To understand the current and potential role of state hospitals in serving geriatric patients, national trends in the use of state mental hospitals by adults age 65 and older were examined. METHODS: State hospital use by older adults in the 50 states and the District of Columbia was compared for the years 1984 and 1993 using published data from the Center for Mental Health Services. RESULTS: Nationally, the number of state hospital admissions and residents declined between 1984 and 1993, and the rate of decrease was greater for older adults than for younger adults. However, states varied considerably in the rate of decrease in the number of older adult state hospital residents and admissions and in the proportion of older adult patients diagnosed with an organic mental disorder. In ten states, the older-adult state hospital population increased. CONCLUSIONS: Although the national trend is toward a declining role for state hospitals in treatment and care of older adults, in several states the hospitals fill an important function in providing custodial care and acute care for this population.