Introduction: Endoscopic sinus surgery can result in serious extraocular muscle dysfunction. The medial rectus muscle is more frequently affected than other extraocular muscles. Methods: A transconjunctival subperiosteal medial orbitotomy was successful in retrieving a partially extirpated medial rectus muscle after endoscopic sinus surgery. Results: A previous attempt to localize this muscle by conventional surgery with extensive exploration was unsuccessful. A Hummelsheim procedure was also abandoned after a rupture of the nasal aspect of the inferior rectus muscle occured. Conclusion: The approach we describe allowed adequate visualization of the posterior orbital content, as well as adequate space for suture placement.