Capillary electrophoresis has been demonstrated to be a new powerful tool for investigating the compositional homogeneity of liposomal membranes composed of phospholipids and guest molecules. In the case of charged components distributed heterogeneously on membranes, electropherograms show several distinguishable peaks even with monodisperse size distributions of liposomes because each liposomal particle carries a different amount of charge. The heterogeneity of noncharged components, when the lipids and the guest components have significantly different molar absorptivities at two different wavelengths, can also be judged from the signal ratio observed at the two wavelengths using a photodiode array detector. This new method can be used for the quality control of liposomal products.