Polyacrylate microlatexes were synthesized by microemulsion polymerization of acrylic monomers in the presence of cationic emulsifiers using a modified process. Paper treated with some of the polyacrylate microlatexes showed good water resistance. Paper's water resistance and its relation to the glass transition temperature (Tg) of the copolymer, the particle size of the microlatex, and the emulsifier were studied. It was found that paper fiber can be uniformly coated by cationic microlatexes with polymers of lower Tg, resulting in higher resistance to water penetration. (C) 2004 Wiley Periodicals, Inc.