To prevent the loss of fiber strength, ultrahigh-molecular-weight polyethylene (UHMWPE) fibers were treated with an ultraviolet radiation technique combined with a corona-discharge treatment. The physical and chemical changes in the fiber surface were examined with scanning electron microscopy and Fourier transform infrared/attenuated total reflectance. The gel contents of the fibers were measured by a standard device. The mechanical properties of the treated fibers and the interfacial adhesion properties of UHMWPE-fiber-reinforced vinyl ester resin composites were investigated with tensile testing. After 20 min or so of ultraviolet radiation based on 6-kW corona treatment, the T-peel strength of the treated UHMWPE-fiber composite was one to two times greater than that of the as-received UHMWPE-fiber composite, whereas the tensile strength of the treated UHMWPE fibers was still up to 3.5 GPa. The integrated mechanical properties of the treated UHMWPE fibers were also optimum. (C) 2003 Wiley Periodicals, Inc.