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A time-of-flight technique has been developed to measure accurately the longitudinal diffusion coefficient (DL) and the drift velocity (v) for electron swarms drifting and diffusing through uniform electric fields at high E/N.A pulse of electrons is released at the cathode, and a `box-carÂ¿ detector system is used to record the anode current distribution. The drift velocity is obtained from the mean delay time, and the longitudinal-diffusion coefficient is obtained from the standard deviation of the distribution. Results have been given for both hydrogen and nitrogen gas for the range 3 Â¿ E/N Â¿ 43 Td (1 Td = 10Â¿21 Vm2). The values for the drift velocity are in good agreement with theory, whereas the values for DL have revealed inadequacies in the present theoretical values for nitrogen.