This article deals with the effect of the monomer ratio on the typical properties of polymer-modified mortars with poly(methyl methacrylate butyl acrylate) latices. Polymer-modified mortars, with methyl methacrylate/butyl acrylate copolymer latices of various methyl methacrylate/butyl acrylate ratios, were prepared with different polymer/cement ratios and were tested for their workability, air content, compressive strength, flexural strength, and water absorption. On the basis of the test results, the effects of the monomer ratio and polymer/cement ratio on the typical properties were examined. The properties of the latex-modified mortars were affected to a great extent by both the monomer ratio and polymer/cement ratio. (C) 2004 Wiley Periodicals, Inc.