Composites made of glass fibers and unsaturated polyester resins are widely applied for various products. The failure processes of such composites are insufficiently understood. Fracture of the resin often initiates bulk composite fracture. Residual stresses occur during the curing of the resin due to the resin volumetric shrinkage. These unfavorable stresses may enhance resin fracture. Moreover, resin shrinkage may decrease the surface quality of the product. The addition of Low Profile Additives (LPA) to the resin may decrease or even remove these problems. The shrinkage behavior of unsaturated polyester resin with varying amounts of LPA is investigated in this work. The emphasis is on the development of curing shrinkage occurring after the gel point of the resin and on accompanying shrinkage stresses. These stresses can be reduced and even reversed by the addition of LPA.