1,2,3,4-Butanetetracarboxylic acid (BTCA) was applied to crosslink amorphous regions of cotton-type rayon fibers via anhydride-mediated esterification for the purpose of a molecular-level control over macroscopic properties. Formation of intrafiber crosslinked structures of the rayon fibers was a facile and efficient method to diminish swelling degree and enhance tensile properties. Crosslinking was conducted under a series of curing temperature and various dosages of BTCA with the presence of sodium hypophosphite as the catalyst for anhydride formation. It was found that crosslinking conditions, both the curing temperature and dosage of the crosslinking agent, made notable impacts on the crosslinking behaviors of the rayon fibers. The dry and wet tensile strength of the rayon fibers were optimized for both the dosage of the crosslinking agent and the curing temperature. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 3553-3559, 2011