16 patients have been treated until October 1987 at the mixed reactor beam of the RENT-facility in Munich-Garching. All of them received a single dose of 200 to 250 cGy after complete conventional radiotherapy and in same cases also surgery because of the lack of complete tumor resection or local tumor control after radiation control. The ages ranged from 40 to 84 years. The follow-up amounted between two and 28 months, 8.5 months on the average. The tumors selected appeared to be particularly suitable because of their growth in poorly perfused tissues, after the previous surgery and/or radiotherapy. All cases are briefly reported. The general experience from the very limited study is promising. The local effects to the tumor tissue so far are impressive. No severe side effects which could be related to the RENT-session were observed until now.