Background and ObjectiveInterstitial photodynamic therapy is a potentially important tool in the management of voluminous or deep-seated recurrent head and neck cancers. Study Design/MethodsThe described treatment algorithm in this manuscript consists of the treatment simulation, implantation of light sources, verification, modification of the treatment plan if necessary, and illumination. The tumor is delineated on imaging sections (CT, MRI, and/or PET/CT) and the treatment is simulated by virtually introducing light sources to the tumor volume on specially modified brachytherapy software. This enables us to determine if the treatment is technically feasible, a ResultsThis method has the potential to help with identifying iPDT feasible patients by simulating before the actual treatment. The suboptimal placement of light sources can be identified and corrected. The simulations were documented and saved for subsequent evaluation of the technique. ConclusionThe proposed technique can help standardize and document iPDT. Lasers Surg. Med. 45:517-523, 2013. (c) 2013 Wiley Periodicals, Inc.