[en] A study was made on possibility of increasing efficiency of radiotherapy of experimental brain tumors using xantobin. Statistically important effect, related with criterion of increase of the average life span (ALS) of animals, was achieved when using both single and fractional irradiation. Metronidazole under experimental conditions didn't produce statistically reliable effect on ALS of rats - tumor-carriers. Xantobin in applied dose was endured satisfactorily by animals; any toxic manifistations were not revealed