Hybrid miniemulsion polymerization was performed with a three-component acrylic system of methyl methacrylate, butyl acrylate, and acrylic acid in the presence of a Bayer(R) Roskydal TPLS2190 unsaturated polyester resin. Latexes were obtained in which the polyester resin was grafted to the acrylic polymer, forming a water-based crosslinkable coating. Grafting between the resinous component and the acrylic polymer is a feature different from the work of others who have attempted to combine the properties of both systems in water-based blends. Both emulsions and latexes were shelf-stable for over 6 months, shear-stable, and resistant to at least one freeze/thaw cycle. Resin-to-monomer ratios were studied as high as 1 : 1 (wt : wt), and total emulsion solids, as high as 45%. Monomer droplet and latex particle sizes were similar, suggesting evidence of the preponderance of droplet nucleation. A high level of crosslinking (>70%) during polymerization was observed in this particular hybrid system in contrast to those involving alkyd or polyurethane resins (<5%). Films, both homogeneous and hard, were achieved with exceptional adhesion. Electron microscopy showed the hybrid particle morphology to have internal domains of polyester resin in an acrylic matrix. (C) 2000 John Wiley & Sons, Inc.