This paper deals with interstitial radiation therapy (RT), interstitial hyperthermia (HT) and interstitial photodynamic therapy (PDT). Its main focus, however, is to describe a single animal model in which the interaction of these three modalities, when applied by interstitial techniques, can be studied. To serve this purpose a special template was designed by which the parallel interaction of catheters (sources) with a fixed spacing was facilitated. If necessary, radiation sources could be fixed into the tumor during the computed treatment time. The applicability of this simple design is demonstrated by the preliminary findings of two conducted pilot studies, that is with the combination of interstitial PDT + HT and the combination of interstitial HT + RT.