Graft copolymerization of methylmethacrylate onto mulberry silk fibers was studied under photoactive conditions with visible light using the Mohr’s salt-potassium persulfate as the redox initiator in a limited aqueous medium. Polymerization in the presence of light at 40 +/-1 degrees C was found to be more pronounced than that in the dark at 40 +/- 1 degrees C. Percent grafting, percent total conversion, and grafting efficiency under different sets of conditions were studied, and the mechanisms of polymerization and graft copolymer formation were discussed. Characterization of the grafted fibers was done by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, and thermogravimetry.