The kinetics of aqueous free-radical graft polymerization of 1-vinyl-2-pyrrolidone onto silica activated with vinyltrimethoxysilane was studied with a mechanistic polymerization model and experimental data for a temperature range of 70-90 degreesC. The polymerization was initiated with hydrogen peroxide with initial monomer concentrations ranging from 10 to 40 Vol %. The kinetic model, which incorporates the hybrid cage-complex initiation mechanism, describes the experimental polymerization data for which the kinetic order, with respect to the monomer concentration, varies from 1 to 3/2. Surface chain growth occurs by both monomer addition and homopolymer grafting, a although the latter contribution to the total polymer graft yield is less significant. Increasing the initial monomer concentration enhances both surface polymer density and average grafted chain length. Increasing reaction temperature, however, produces a denser surface layer of shorter polymer chains.