A novel technique has been devised to characterize dielectric relaxation in transfer media, for better prediction of performance in electrostatic transfer of developed toners to receiving media. In this process, efficient dielectric relaxation in the media enables efficient transfer at moderate bias voltages. A recent theoretical analysis has shown that dielectric relaxation in transfer media is determined, not simply by sample resistance and capacitance, but more precisely by charge density, charge mobility and charge injection properties. In the new characterization technique, the observed decay of voltage over an electrostatically charged sample is interpreted in terms of these transport parameters. Results from representative media samples are presented and discussed.