Interfacial tension has been determined for phosphatidylcholine-cholesterol, phosphatidylcholine-phosphatidylethanolamine, and phosphatidylethanolamine-cholesterol membranes. Phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cholesterol (Ch) were to be investigated, because of their presence in biological membranes. Interfacial tension values of pure components are 0.81 × 10–3 N/m, 1.67 × 10–3 N/m, and 2.36 × 10–3 N/m, respectively. The 1:1 complexes were formed during formation of the PC–Ch, PC–PE, and PE–Ch lipid membranes. The following parameters describing the complexes were determined: A3–1, the surface concentrations of the lipid membranes formed from these complexes; γ3, the interfacial tensions of such membranes and K, the stability constants of these complexes. [ABSTRACT FROM AUTHOR]