Constant temperature and pressure (NPT) atomistic molecular dynamics (MD) simulations have been carried out on fully hydrated liquid crystalline lamellar phase of a pure dimyrystoylphosphatidylcholine (DMPC) lipid bilayer at 30 degreesC, and its mixture with a mol fraction of 12.5% of ethanol. It has been observed that at this low concentration the ethanol molecules preferentially occupy regions near the bilayer interface, in agreement with NMR data. Small changes in bilayer structure and the lipid hydrocarbon chain conformations have been noticed. It is observed that the interaction between the ethanol molecules and the lipid head groups has influence on the orientation of the P- --> N+ head group dipole toward the aqueous phase. (C) 2004 Elsevier B.V. All rights reserved.