Sonication of a non-ionic polymerizable chlosterol-based amphiphile, 1-ethenyl-3-(8-(cholest-5-en-3beta-yloxy)-3,6-dioxaoctyl)-2?? -pyrrolidone, in water resulted in the formation of bilayer vesicles. The vesicle formation was evidenced by transmission electron microscopy and [C-14] sucrose entrapment. Polymeric vesicles, prepared by polymerization in the bilayer, showed increased stability.