In this paper, we have looked at mental hospital decentralization as it has developed in the thirteen State of Illinois mental hospitals as of June 30, 1967. The hospitals were looked at from the most centralized to the most decentralized. This was done by relating the hospitals to five descriptive model types, described at greater length elsewhere. Hospital decentralization is portrayed as a complex and highly idiosyncratic process. Attempts to place specific hospitals at point along the decentralization continuum are thus tentative and clear rules for classifying stages of decentralization have yet to be formulated. Complicating the picture still further is that hospitals in transition change rapidly and may at even intervals of a month show dramatic change. It is expected that the trend implied is stable, however, and that ultimately all Illinois state mental hospital with possible exception of ISPI and Illinois Security Hospital, will be located at the decentralized model. This is seen as necessary if they are to survive as viable treatment institutions.