Ultrahigh molecular weight polyethylene (UHMWPE) has high yield strength and modulus, but is nonpolar and chemically inert. For it to be used as an effective reinforcing agent for composites, methods to make the UHMWPE wettable or capable of reaction with the matrix are critical. In the current work, Spectra 900 (TM) (UHMWPE) fibers were surface modified by swelling in p-xylene with: (1) methylmethacrylate (NIMA) monomer; (2) PMMA; (3) camphorquinone (CQ); (4) 3-methacryloxypropyltrichlorosilane (Cl-MPS); (5) trimethoxysilyl modified polyethylene, N-(triethoxysilylpropyl)-dansylamide (fluorescent silane), or octadecyltrimethoxy silane (OMS), followed by hydrolysis and reaction with Cl-MPS, and (6) by coating with SiO2 films followed by reaction with MPS. These modifiers were used to improve wettability and provide sites for chemical interactions with the resin matrix. Beads of resin [60/40 BisGMA-TEGMA (bis-phenol A bis-(2-hydroxypropyl) methacrylate and tri(ethylene glycol) dimethacrylate)] were light-cured around the treated fibers and the improvement in adhesion was tested by microbond shear strength (tau) tests. The improvements were comparable to those reported by acid etching and plasma treatments. The OMS, fluorescent silane, and SiO2/Cl-MPS treatments yielded the best results, that is fourfold increases in tau compared with untreated fibers. (c) 2005 Wiley Periodicals, Inc.