Radiation therapy has been used in the treatment of numerous head and neck malignancies. Unfortunately, this treatment also causes complications by increasing the morbidity to the surrounding tissues. The fabrication of a tissue bolus prosthesis is recommended to compensate for the loss of tissue and to help distribute the radiation homogeneously to the tissues. This article describes the procedures necessary for making an impression and fabricating a tissue bolus prosthesis. This custom-made prosthesis is simple, efficient, and atraumatic for the patient. Use of a tissue bolus prosthesis allows the radiation oncologist to adequately irradiate the tissues. (J Prosthet Dent 2000;83:119-21.).