In our studies with simulated extracorporeal blood circulation we observed damaging effects on blood cells, especially under oxygenating conditions. In order to characterize these effects we also analysed electrolyte and trace-element concentrations in plasma during and after simulated extracorporeal blood circulation. Highest resorption effects for magnesium and highest desorption effects for calcium, copper and iron are found with oxygen gas flow in the system. Membrane permeability for electrolytes seems to be induced as well. Cellular damage due only to mechanical stress within the perfusion system can be neglected.