The surfactant-free synthesis of poly(methyl methacrylate)-silica nanocomposite particles has been achieved in aqueous alcoholic media at ambient temperature without the use of auxiliary comonomers. Stable colloidal dispersions with reasonably narrow size distributions can be obtained with silica contents of up to 58% by mass. X-ray photoelectron spectroscopy and aqueous electrophoresis studies indicate that these nanocomposite particles have silica-rich surface compositions.