The main objective of this research was to investigate the effect on thermal properties of the addition of two different compatibilizing agents, maleic anhydride (MA)-grafted polypropylene (MAPP) and MA-grafted polyethylene (MAPE), to bio-flour-filled, Polypropylene (PP) and low-density polyethylene (LDPE) composites. The effect of two different types of MAPE polymer, MA-grafted high-density polyethylene (HDPE-MA) and MA-grafted linear LDPE (LLDPE-MA), was also examined. With increasing MAPP and MAPE content, the thermal stability, storage modulus (E'), tan delta(max) peak temperature (glass transition temperature: T-g) and loss modulus (E"(max)) peak temperature (beta relaxation) were slightly increased. The thermal stability, E' and E' of MAPE-treated composites were not significantly affected by the two different MAPE polymers. The melting temperature (T-m) of the composites was not significantly changed but the crystallinity (X-c) of MAPP- and MAPE-treated composites was slightly increased with increasing MAPP and MAPE content. This enhancement of thermal stability and properties could be attributed to an improvement in the interfacial adhesion and compatibility between the rice husk flour (RHF) and matrix due to the treatment of compatibilizing agent. Attenuated total reflectance (FTIR-ATR) analysis confirmed this result by demonstrating the changed chemical structures of the composites following MAPP and MAPE addition. (C) 2006 Elsevier B.V. All rights reserved.