The educational experience in the operating room is considered the centerpiece of learning for surgical residents. The educational environment is defined as the "ethos" or "climate" that affects all aspects of learning within an educational setting. A measure of the educational environment in the operating room as perceived by residents would assist educators and trainees in gauging the quality of the learning occurring within this important venue. The Operating Room Educational Environment Measure (OREEM) was adapted from an inventory validated for use with basic surgical trainees in Scotland to determine whether an inventory specifically adapted to the specialized environment of the operating room can produce a valid assessment of trainee perception of the overall educational environment and the contributing factors therein at a North American institution. The 40-item inventory was piloted on a group of general surgery residents at the University of Calgary from November 26, 2003, to January 31, 2004. With a response rate of 96%, the OREEM was shown to be a relevant, internally consistent (Cronbach proportional, variant = .8656) and valid tool for assessing the overall educational environment in the operating room within a Canadian surgical residency program. Four subscales included teaching and training, learning opportunities, atmosphere, and workload/supervision/support. The overall mean score of 74% suggests the learning environment may be considered satisfactory; however, areas for potential improvement are identifiable. Results reveal strengths such as a nondiscriminatory operating room atmosphere on racial and gender grounds. However, differences were shown in male and female perceptions of learning opportunities and in junior versus senior perceptions of workload, supervision, and support. The OREEM has potential to be applied further as a quality assessment tool whose results could be used by faculty and program directors to improve the learning experiences of residents in the operating room.