Dynamic shear moduli of multibranched polystyrenes were measured as functions of frequency and temperature using a parallel-plate rheometer. The multibranched polystyrenes are poly(macromonomer)s of omega-methacryloyloxyethyl polystyrene macromonomers (MA-PSt)s and statistical copolymers of the MA-PSt with methyl methacrylate (MMA) monomer. The master curve of the storage dynamic shear modulus G＇ for the poly(macromonomer)s did nor show the so-called plateau region and the G＇ gradually decreased from the edge of the glass transition region to the terminal zone and the loss modulus G " was always larger than G＇. The plateau region became clear in the copolymers with less branch density. These results indicate that the intermolecular chain entanglement might be strongly restricted in the poly(macromonomer) systems due to the multibranched structure of high branch density, which also explains the brittle property of the poly(macromonomer) films. (C) 2000 Elsevier Science Ltd. All rights reserved.