A free radical thermoset resin consisting of a copolymer of conjugated linseed oil (CLO) or conjugated soybean oil (CSO), n-butyl methacrylate (BMA), divinylbenzene (DVB), and maleic anhydride (MA) has been reinforced with rice hulls. Composites containing 70 wt % of the filler were compression molded, the conjugated oil content in the resin was kept constant at 50 wt %, and the relative amounts of BMA, DVB, and MA were varied to afford composites with different resin compositions. Tensile tests, DMA, thermogravimetric analysis, and Soxhlet extraction of the different composites prepared have been used to establish the relationship between resin composition and the properties of the composites. Overall, the mechanical properties tend to improve when MA is introduced into the resin. Scanning electron microscopy of selected samples showed a better filler-resin interaction for MA-containing composites and samples prepared from CLO exhibit better properties than those prepared from CSO. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121:2050-2059, 2011