An improved collector structure is disclosed which is adapted for use in electrostatic precipitators to increase the efficiency of operation by increasing the electric field uniformity in the device and by reducing the power consumption without appreciably increasing reentrainment of the precipitated particles during operation. The collector is provided with an insulating material of the type which has an electrical relaxation time, .rho..epsilon., that is preferably greater than that associated with the particle current in the gas near the collector electrode, a triboelectric rank that is as low as possible if the collector electrode is negatively charged or as high as possible if the collector electrode is positively charged with respect to the opposite electrode and a thickness and resistivity such that the voltage drop across the insulation does not exceed about 5 to 10% of the applied voltage between the oppositely charged electrodes of the precipitator. A modification of the apparatus includes a mesh or screen grid structure attached to the exposed surface of the insulation.