Poly(styrene-co-acylonitrile) was used to modify diglycedyl ether of bisphenol-A type epoxy resin cured with diamino diphenyl sulfone and the modified epoxy resin was used as the matrix for fiber-reinforced composites (FRPs) to get improved mechanical properties. E-glass fiber was used as fiber reinforcement. The tensile, flexural, and impact properties of the blends and composites were investigated. The blends exhibited considerable improvement in mechanical properties. The scanning electron micrographs of the fractured surfaces of the blends and tensile fractured surfaces of the composites were also analyzed. The micrographs showed the influence of morphology on the properties of blends. Results showed that the mechanical properties of glass FRPs increased gradually upon fiber loading. Predictive models were applied using various equations to compare the mechanical data obtained theoretically and experimentally. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3431-3438, 2008