We report the first endoscopic surgeries performed with patients under general anesthesia using intraoperative guidance with MRI. The procedures were experimental and intended to test (1) the unusual working environment of a unique new "open-configuration" MRI unit for head and neck surgery, and (2) real-time image guidance. Twelve patients underwent endoscopic sinus surgery while under general anesthesia in a new open MRI unit that provides the surgeon with access to the patient while imaging is performed. Eleven patients had chronic sinusitis (eight of them had bilateral disease), and one had a right nasoethmoid and antral tumor. All 12 surgeries were performed without complications. Both the endoscopic view and the MRI scans were available at the surgical field. The image plane was surgeon controlled, and the MRI updated images in as little as 14 seconds. MRI provided adequate visualization of both the disease and the related anatomy and allowed the surgeon to navigate during the procedure. The intraoperative data reflect the tissue changes during surgery and provide optimum feedback for surgical guidance. Although the operating environment poses some limitations, it has become apparent that intraoperative MRI has a role in the treatment of head and neck disorders and warrants further study.