Prolonged soft tissue compression results in discomfort and pain secondary to local ischemia in normal individuals. During surgery, patients are immobile and unable to perceive the discomfort of prolonged pressure, and the anesthetized patient lacks a protective mechanism to prevent pressure sores. Many intrinsic and extrinsic factors are associated with pressure sore development; however, the intensity and duration of pressure are critical components in the etiology of pressure sores. We conclude that interface pressure on a patient lying on an operating table during a long operation is a primary factor of postoperative occipital pressure sores.