OBJECTIVE: Endoscope-guided round window membrane repair was performed to evaluate whether the approach is feasible in the treatment of a round window fistula. STUDY DESIGN: Retrospective case review. SETTING: Tertiary care academic center. PATIENT: A 27-year-old man had been scuba diving 6 days previously in the Australian Great Barrier Reefs. He had poor hearing with tinnitus in the left ear and a vertiginous sensation. INTERVENTION: A myringotomy was incised, and a tympanoscope was introduced into the middle ear cavity. With the patient under general anesthesia, the middle ear and the oval and round window areas were examined with a tympanoscope. In endoscopic visualization, a round perforation could be seen in the round window membrane. After detection of the round window perforation, a small piece of temporal fascia was obtained to seal the membrane perforation. RESULTS: One month after the operation, the patient's hearing was significantly better. The myringotomy had healed. CONCLUSION: A transmyringeal endoscopic procedure for round window fistula repair is feasible and combines the best features of minimally invasive surgery and aural endoscopy.