The properties of reactive hot melt polyurethane adhesives (RHAs) modified by dihydroxyl-terminated reactive acrylic macromonomers were examined and compared with those of RHAs modified with a nonreactive commercial acrylic copolymer. The melt viscosity and initial bond strength was increased when a portion of the polyols and tackifier was replaced by macromonomers or acrylic copolymers, which have higher glass transition temperatures. When RHA was modified by macromonomer, the storage modulus at low shear rate was reduced and set time was increased, which suggests that the chain entanglement was diminished by short-chain branches created by the macromonomers. (C) 2008 Wiley Periodicals, Inc.