A general hospital based psychiatric acute observation and treatment unit is described, and its operation over a one year period is reviewed. This seven-bed unit is designed to provide constant nursing observation and management, as well as intensive psychiatric treatment, in a secure, safe, and quiet environment for the most acutely psychiatrically ill patients. During the year under review, the unit had 330 admissions. Demographic, clinical, and treatment data are presented, and management of disturbed behavior, staff selection, and acceptance of the unit are discussed.