Acrylonitrile butadiene rubber (NBR)-based composites were prepared by incorporating short nylon fibers of different lengths and concentration into the matrix using a two-roll mixing mill according to a base formulation. The curing characteristics of the samples were studied. The influence of fiber length, loading, and rubber crosslinking systems on the properties of the composites was analyzed. Surface morphology of the composites has been studied using Scanning Electron Microscopy (SEM). Addition of nylon fiber to NBR offers good reinforcement, and causes improvement in mechanical properties. A fiber length of 6 mm was found to be optimum for the best balance of properties. It has been found that at higher fiber loadings, composites show brittle-type behavior. Composites vulcanized by the dicumyl peroxide (DCP) system were found to have better mechanical properties than that by the sulfur system. The swelling behavior of the composites in N,N-dimethyl formamide has been analyzed for the swelling coefficient values. Composites vulcanized in the DCP system were found to have higher rubber volume fraction than that in the sulfur system, which indicates better rubber-fiber interaction in the former. The crosslink densities of various composites were also compared. (C) 2004 Wiley Periodicals, Inc.