A 100 ns simulation of a fluid phase dioleoylphosphatidylcholine bilayer, consisting or 288 lipid molecules at. full hydration, has been Studied to describe in detail the lateral translational motion of individual lipid molecules. Analysis of the simulation trajectories suggests that correlated motion between neighboring lipid molecules is ail important aspect of lipid dynamics. The correlation among neighboring lipids within a monolayer is substantial and Surprisingly long-ranged with a decay length of approximately 25 angstrom. This provides a mechanism for the previously published observation that lateral diffusion coefficients computed from molecular dynamics simulations exhibited a strong dependence oil the size Of the unit cell and for the recent suggestion that lipid flows on that nanoscale are an important component of translational diffusion within membranes. Additionally, we show that diffusive motion is only weakly correlated between lipids in opposing monolayers.