Epoxy composites incorporating natural components have been mainly limited to the use of natural fibers. However, there have been a few instances where polysaccharides have been used as particulate fillers in thermoset compositions. The present study investigated the effect of guar gum/hydroxypropyl guar gum as a filler on the degradative properties of epoxy composites at various filler concentrations, with reference to fungal degradation and soil burial tests. It was found that at higher filler concentrations, the degradation increased. Composites based on hydroxypropyl guar gum showed increased degradation initially but on prolonged exposure to the fungal environment, the difference between guar gum and the hydroxypropyl guar gum-based composites was found to be marginal. Microscopic evaluation of the composites showed that the degradation occurred at both the composite surface and in the bulk. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 1494-1500, 2009