A versatile non-aqueous emulsion polycondensation process for the mild fabrication of polyester nanoparticles is presented. Spherical nanoparticles with diameters smaller than 60 nm are prepared in non-aqueous emulsion systems. These emulsions consisted in one case of DMF dispersed in n-hexane and in a second with acetonitrile dispersed in a continuous cyclohexane phase. Stabilization of these systems was achieved by using a polyisoprene-polymethylmethacrylate block copolymer. The suitability of these aprotic emulsions for synthesizing polyester nanoparticles by emulsion polycondensation having molecular weights up to 22,000 g/mol is demonstrated, (c) 2006 Wiley Periodicals, Inc.