Endotoxin incorporated into liposomes, lipid bilayers or lipid complexes can be detected by combining an aqueous suspension of the liposomes, lipid complexes or lipid bilayers with a suitable detergent. Preferable detergents, e.g., Lubrol-PX.TM. or a polyoxyethylene ether, solubilize the lipid bilayers, liposomes or lipid complexes at acceptable lipid concentrations, forming micelles therefrom which contain lipid bilayer, liposome or lipid complex lipid, detergent and endotoxin, should it be present. The micelles are then assayed for the presence of endotoxin.