A previous study showed that it was feasible to use wood fibers obtained from palm-tree branches to reinforce polypropylene. It was the objective of this study to investigate the moisture-sorption characteristics of palm-fiber/polypropylene composites and the effect of using a compatibilizer on that important material property. The results of the investigation showed that the amount of moisture absorbed at saturation by polypropylene during immersion in distilled water and various salt solutions increased significantly with the introduction of palm fiber into the polymer. On the other hand, the use of maleated (maleic anhydride modified) polypropylene (Epolene E-43) as the compatibilizer did not have a significant effect on the amount of Moisture intake of palm/polypropylene composites at satu-ration. However, there was a significant change in the moisture-diffusion rate with the incorporation of the Epolene E-43 compatibilizer into the composites: the compatibilizer resulted in a significant increase in the diffusion rate. The rnoisture diffusivity was not affected by the solution type for the palm/polypropylene composite specimens without any compatibilizer, but some increase in the mass diffusivity was observed as the purity of the solution increased (as the salt concentration decreased) when the Epolene E-43 compatibilizer was used in the palm/polypropylene composites. (c) 2007 Wiley Periodicals, Inc.