To reveal the influence of glass transition temperature of matrix polymer on electric resistivity and electrical response to organic solvent vapors of carbon black (CB) -filled polymer composites, conductive CB/poly (methyl methacrylate), CB/poly(butyl methacrylate) and CB/poly(2-ethyl hexyl methacrylate) composites were fabricated by polymerization filling. It is found that the composites obtained exhibit a lower percolation threshold and a slower electrical response rate when the glass transition temperature of the matrix polymer is higher. Because the dispersion status of CB particles in the composites is related to the glass transition temperature or viscosity of the matrix polymer, and influences the composite conductivity. Low viscosity of the matrix polymer would certainly benefit the diffusion of solvent molecules in the matrix polymer and decrease the response time of the composites against organic vapors. These results would help to choose a suitable polymer as the polymer matrix and to understand the electrical response behavior of the composites as promising gas-sensing materials. (C) 2008 Elsevier B.V. All rights reserved.