Reactive cement-in-polymer dispersions have been prepared from poly(vinyl alcohol), poly(ethylene-co-vinyl acetate), and poly(vinyl acetate) and a non-hydrated, fine-grained cement, and used to coat multifilament glass-rovings. The influence of the molecular properties of the polymer, such as the chemical composition and molecular weight as well as the cement content in the dispersion, on the reinforcing performance of the coated rovings in concrete has been studied using scanning electron microscopy and tensile tests. All coated rovings significantly surpass the uncoated glass in terms of mechanical behavior. The best bonding was obtained with hydrophobic, PVAc-based coatings, since the slow hydrolysis and swelling of this polymer controls cement hydration and the formation of the interphase. The mechanical behavior of the coated rovings is barely influenced by the molecular weight of the polymer, but decreases with decreasing cement content. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 3303-3309, 2010