Two surface modification methods-plasma surface treatment and chemical agent treatment-were used to investigate their effects on the surface properties of ultrahigh-molecular-weight polyethylene (UHMWPE) fibers. In the analyses, performed using electron spectroscopy for chemical analysis, changes in weight, and scanning electron microscope observations, demonstrated that the two fiber-surface-modified composites formed between UHMWPE fiber and epoxy matrix exhibited improved interfacial adhesion and slight improvements in tensile strengths, but notable decreases in elongation, relative to those properties of the composites reinforced with the untreated UHMWPE fibers. In addition, three kinds of epoxy resins-neat DGEBA, poly-urethane-crosslinked DGEBA, and BHHBP-DGEBA-were used as resin matrices to examine the tensile and elongation properties of their UHMWPE fiber-reinforced composites. From stress/strain measurements and scanning electron microscope observations, the resin matrix improved the tensile strength apparently, but did not affect the elongation. (c) 2007 Wiley Periodicals, Inc.