The synthesis of Au and Co/Co(OH)(2) nanoparticles has been accomplished with the use of polymerized vesicles composed of mixtures containing 10% or 50% (w/w) of a palladium ion bound negatively charged phospholipid, 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphohydroxyethanol, and a zwitterionic phospholipid 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine. The divalent palladium ion bound to the negatively charged phospholipids in the polymerized vesicle membrane initiated electroless metalization of gold or cobalt on the vesicle surface leading to the formation of metallic nanoparticles. The particles have been characterized by transmission electron microscopy(TEM), high-resolution transmission electron microscopy (HRTEM), and electron diffraction. Polymerized vesicles containing catalytic sites only on the external membrane surface were partially metalized with crystalline gold particles. By use of the internal volume of polymerized vesicles as the reaction vials, two types of unagglomerated nanoparticles (4-10 nm), Au and Co/Co(OH)(2), have been synthesized. HRTEM studies have demonstrated that particle nucleation and-growth occurred within the vesicles and that particle growth could be initiated by either single or multiple nucleation sites.