The search for ways to overcome tumour radioresistance is a major problem of experimental and clinical radiation oncology. The diffi- culties involved in the attempts to solve this problem are a matter of common knowledge. In many a laboratory extensive studies are un- derway of factors determining tumour tissue response to irradiation and of methods for exerting directional effect upon those factors. Such studies have revealed that, at least at the cellular level, a considerable number of factors manifest themselves which are respon- sible for radiation effect (1] * Among those are: spatial...