The main components of cell membranes are phospholipids and proteins. The aim of our study was to examine structural changes of dipaimitoyl-phosphatidylcholine (DPPC) monolayer as a simple model system of a cell membrane in different environments. Pure water, ethanol and methanol solutions were used as subphases of Langmuir films as a membrane models. For detection of changes in charge states of the molecules as well as relation with structural and conformational changes, a contactless method Maxwell's displacement currents (MDC) was used. Behaviour of DPPC molecules on two different subphases is substantialy different. In DPPC monolayer on the subphase of methanol-water, a gradual absorption (incorporation, penetration) of methanol molecules into the layer can appear. In DPPC monolayer on the subphase of ethanol-water adsorption of ethanol molecules on the layer can be observed. The membrane permeability might change. At both subphases (ethanol-water and methanol-water) the elasticity modulus of the monolayer decreases leading to the loss of membrane elasticity. (c) 2006 Elsevier B.V. All rights reserved.