The absorption of D-glucose by rat thymocytes is reduced to half of control by 30 mumol/L and decreased to 10% by 100 mumol/L of RE 1492. This is backed by the fact that the absorption of 2-deoxy-D-glucose is inhibited in the same extent. The more hydrophilic oligoamine RE 1888 had an analogous but smaller effect while spermine was ineffective. In a lipid peroxidation model RE 1492 or spermine in a concentration of 100 mumol/L nearly completely inhibited for formation of Fe3+ ions when the phospholipid was mimicked by adenosine monophosphate. This suggests an interaction with negatively charged membrane phospholipids. RE 1888 had an equal but smaller effect. The effect of RE 1492 on lipid order and lipid motility was checked on ovine lymphocyte membranes by fluorescence polarization measurements. The steady state as well as the limiting anisotropy as an expression for lipid order is decreased by rising concentrations of RE 1492. The use of several anthroyloxy stearic acids as fluorescent probes also shows an increased lipid motility in several areas of the membrane bilayer. The use of fluorescent parinaric acid suggests that areas of high regularity, i.e. liquid crystal formation are involved, too.