The author attempted to determins whether hospitals of the same type, with similar admission and discharge policies and operating under identical regulations, had similar patterns of use of seclusion and restraint. Admissions to seven Massachusetts state hospitals over a two-week period were followed until discharge or up to 16 weeks. The hospitals were found to use confinement to widely varying degrees that could not be explained by patient demographic characteristics, legal status, diagnoses, or violence-related behavior preceding hospital admission. The author suggests that factors relatting to individual hospital practices and conditions strongly influence the use of confinement. He discusses the implications of this conclusion.