Abstract: The detrimental effects of reinforcing fibers on the differential shrinkage and warpage characteristics of thermoplastic resins are substantially reduced by the incorporation of a silicone interpenetrating polymer network in fiber reinforced thermoplastic composites. High modulus (flexural modulus greater than 90,000 psi) thermoplastic matrices containing about 5 to 60 weight percent reinforcing fibers and 1 to 20 weight percent of a silicone IPN have reduced shrinkage and warpage and more isotropic mold shrinkage than conventional fiber reinforced thermoplastics, and are particularly useful in the melt forming of high tolerance parts, such as gears, as well as thin walled, variable thickness and thick cross section parts.