The kinetics of interaction of aqueous suspensions of phosphatidylethanolamine derivatives with single bilayer egg yolk phosphatidylcholine (egg PC) vesicles has been studied. For this purpose 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) was reacted with the free amino group of l-α-phosphatidylethanolamine, -dilauroyl and -dimyristoyl to give N-NBD-DLPE (Ia) and N-NBD-DMPE (Ib). Electron microscopy and 31P-NMR experiments performed with (Ia) indicated that the labeled lipids in aqueous buffer are present in the form of nonbilayer aggregates of 100–200 Å diameter with a highly disordered headgroup arrangement. The time-evolution of the NBD emission intensity in the incubation mixtures of (I) with small and large unilamellar vesicles (SUV and LUV) could be fitted with a double exponential function. The fluorescence decay parameters of the NBD group changed during the reaction time of (I) with SUV but did not change when aggregates of (I) were mixed with LUV. A kinetic model was evaluated which assumes the adsorption of aggregates of (I) to the surface of the liposomes in a primary step. The relaxation characteristics of this heterogeneous lipid distribution towards a more homogeneous membrane structure can be explained by the presence of two non-fluorescent pools of (I) and a fluorescent one in the egg PC matrix. The rate constants for transfer of (I) between those kinetic pools as well as equilibrium emission intensities were found to decrease with increasing length of the fatty acid chains of (I). This behaviour was explained by differences in the properties of the clusters of (I) in the egg PC membranes.