In recent years there has been a strong movement to replace outdated and inadequate jails throughout the United States. According to the National Sheriff's Association 15.9% of all jails have been under a court order to improve services or conditions at one time or another. In addition, 960 jails of the 3,493 existing jails in the United States were built prior to 1950. This need for new construction or renovation has given birth to a new area of expertise among architects and contractors--jail design and construction. While design and construction techniques have improved, little is known of the effects of physical environment on the social climate of a jail. This research seized upon a natural experiment in which an old, antiquated jail (Rocky Butte Jail) was replaced by a new, ultra-modern 470 bed high-rise jail (Multnomah County Detention Center). The question of what kind of physical environment change affects the social climate of a jail has broad implications with regard to design and construction of jails and other secure facilities. If the answer to this question can be determined, then it may be possible to provide improved service delivery in local jails, increase staff satisfaction with the work environment of jails, and improve mental and emotional health of jail staff and inmates; all of which can be translated into savings to the taxpayer. This study is a pre- and post-event research investigation that used the Rocky Butte Jail and the Multnomah County Detention Center as the setting for this inquiry. The Sonoma County (California) and Salt Lake County (Utah) jails served as control jails. The Correctional Institution Environmental Scale was administered to 877 inmates and staff in the four jails in 1983 and 1984. While the evidence is somewhat inconclusive, the Analysis of Covariance suggests that the inmates and staff as a group believe that there is a positive social climate in the Multnomah County Detention Center. This is expressed in terms of perceived support from fellow inmates and fellow officers and that the jail is orderly and well managed. In addition, inmates and staff as separate groups and in toto have a clear perception of what is expected of them. More important, perhaps, is the indication that well written and clear Policies and Procedures contribute greatly to the orderly management of an institution of this size. Finally, the data leads one to the conclusion that it may never be possible to gain a complete grasp of social climate in an institution of this nature. In general, this research provides a contribution to the literature and to future discussions of jail construction and design.