A molecular dynamics (MD) study of a hydrated phospholipid bilayer is reported. Therein the stability of initially formed water pores in phospholipid membranes is investigated by means of computer experiments based on a microscopic membrane model. The pore lifetimes were found to be in the range of 100 ps. The probability of finding water molecules in the hydrophobic interior of the membrane is discussed. Our results give evidence for the existence of water pores in phospholipid membranes which are sufficiently thin. (C) 2002 Published by Elsevier Science B.V.