Blowout fracture of the medial orbital wall is frequently seen in association with fracture of the floor of the orbit. An isolated blow out fracture of the medial orbital wall with entrapment of the medial rectus muscle is uncommon. There are only 8 such reported cases in world literature until 1974. This is an additional report of one such case. A 15-year-old boy presented with and isolated blowout fracture of the medial wall plus entrapment of the medial rectus muscle. The diagnosis was made with tomography and muscle traction test. At surgery the musle was freed from its entrapment.