Photodynamic therapy (PDT) is a site-specific tumor treatment involving the administration of a photosensitizer activated by the local application of light. In interstitial PDT (IPDT), multiple laser fibers are inserted into the depth of the tumor. Image guidance is essential for accurate, safe, and uniform light delivery. We report a novel technique of IPDT for advanced head and neck tumors involving an open interventional MR system. Initial results are encouraging, with minimal procedural morbidity, successful palliation of symptoms, and prolongation of expected survival time.