The effects of 5 MeV electrons and of gamma irradiation at 0 ~ as well as the effects of 2.45 GHz microwaves at -196 ~ on the osmotic resistance of human erythrocyte membranes are presented. Both electron and gamma radiation in the range 0-400 Gy induced no haemolysis, indicating that the membrane modifications due to radiation interaction do not reach a critical point to cause swelling of the cells and consequent lysis. The microwave irradiated erythrocytes showed a haemolysis degree between 6-16% in the irradiation time range of 0-5 min. The osmotic stress experiments performed after irradiation showed that the gamma irradiated erythrocytes exhibited an almost similar behaviour at all irradiation doses whereas the electron irradiated samples showed a much larger increase in the haemolysis degree, and in the case of a certain electron dose (100 Gy), the haemolysis was found much smaller than for the control sample. A similar behaviour of the erythrocytes was found in the case of microwave irradiation of the cryoprotected erythrocytes at -196~ the sample irradiated for 6 min developed a haemolysis degree much smaller than for the control (70% from the nonirradiated sample haemolysis). Our experimental data suggest that electron radiation and gamma radiation have different impacts on the erythrocyte haemolysis in the dose range used. Much more experimental data is necessary in order to clarify the similarity between the results obtained in the case of electron irradiation at 0 ~ and microwave irradiation at -196 ~ in the two different sets of irradiation conditions (liquid samples at 0 ~ and frozen samples at -196 ~ IntroductionThe impact of high energy electrons on the biological systems is very rarely treated in the published literature [5]. The aim of this paper is to study the differences in the impacts of 5 MeV electrons and gamma radiation, at 0 ~ as well as the effects of 2.45 GHz microwaves at -196 ~ on the osmotic properties of human erythrocyte membranes. The relative rate ofhaemolysis is a well known parameter accounting for the osmotic properties of the erythrocyte membranes [2]. Haemolysis is the process of pore forming in the erythrocyte membrane which allows to release haemoglobin into the external medium of the cells. Radiation studies performed with X rays suggested that radiation induced haemolysis is an osmotic haemolysis, due to the partial destruction of the membrane permeability [6]. In our work, the modifications of the erythrocyte membranes properties were estimated by measuring the haemolysis induced by radiation in the samples and the haemolysis induced experimentally by osmotic stress on the irradiated erythrocytes.