BACKGROUND "Trap door" orbital floor fractures are usually seen in children. In the linear fracture type, a break occurs in the bones of the orbital floor that permits orbital tissue to prolapse into the fracture site during fracture formation. The bony fragments of the fracture then return to their original position, entrapping the prolapsed orbital tissue. In the hinged fracture type, the fractured part of the floor is minimally displaced into the maxillary sinus and acts as the hinge of a "swinging door" entrapping the orbital tissue. METHODS We report on a series of 10 adult patients with hinged orbital floor fractures. RESULTS The mean patient age was 35 years. Seven patients had a pure orbital floor fracture and the remaining 3 patients had fractures of both the orbital floor and the inferior orbital rim. All 10 patients had diplopia in the upgaze. None of the patients had signs of the oculocardiac reflex. None of the CT scans showed a "tear-drop" sign. However, the sagittal CT scans showed evidence of entrapment of the inferior rectus. All patients had a small area of a slightly depressed orbital floor at the site of entrapment, without a bony defect. All patients underwent surgery through an infraorbital incision and a titanium mesh was used in all patients. There were no postoperative complications. All patients regained full range of motion of the globe. CONCLUSIONS This is the first series in the literature that reports on the characteristics and outcome of trap door orbital floor fractures in adults.