The introductory paper to the pathophysiology session of the 19th Annual Meeting of European Society for Radiation Biology, 1985, outlines cell membrane-related phenomena elicited by lower doses of low LET radiations than the cell killing one. Through micromorphological appearances, functional activities like that of receptors and binding sites, early appearing temporary alterations are demonstrated. It is suggested that the injuries of cells, cell-to-cell and cell-to-extra-cellular matrix contacts, the disabled conditions of surviving cells contribute to the development of non-stochastic effects in tissues.