Provided are dispersions which comprise more than about up to 55 percent by weight or more of an organic peroxide which is normally solid in an anhydrous liquid phase such as dibutyl maleate or dioctyl adipate, with about 5% by weight or more fumed silica to provide a thixotropic, storage stable organic peroxide paste. Addition of about 5 weight % or more of fumed silica was found to result in the formation of a shear thinning anhydrous dispersion of organic peroxide which was storage stable.