Abstract: Aqueous dispersions of normally solid, organic polymeric particles are prepared by (1) dispersing an oil phase containing at least one emulsion polymerizable monomer such as styrene in an aqueous phase containing a stabilizing emulsifier such as sodium dodecyl benzene sulfonate and a polymer of a sulfohydrocarbyl ester of an .alpha., .beta.-ethylenically unsaturated carboxylic acid such as a 2-sulfoethyl methacrylate/n-butyl acrylate copolymer and (2) subjecting the dispersion to emulsion polymerization. Microspheres having liquid centers and seamless rigid walls of a normally solid, organic polymer are prepared according to the above method except that the starting oil phase also contains a non-polymerizable, water-insoluble liquid such as hexane.