The rapid decrease in the resident population ofstate hospitals over the last decade has engendered a debate over the future role of the state hospital in the overall mental health services system. The authors report on a 1979 study of more than 2,000 state hospital patients designed to evaluate the characteristics of the current hospital population. Theirfindings document the existence ofa new long-stay population that in many ways is similar to the old long-stay population that existed before deinstitutionalization. Continued hospitalization of the new population of long-stay patients, who now are younger than the old long-stay patient group, could cost more than $ 500 million dollars a year. The authors discuss the difficulty in predicting future trendsfrom the existing data and outline four areas for future re-search.