Some time ago a research programme on the electric strength of pure liquids was started and has led already to a number of publications dealing with the strength of simple organic liquids. In the paper are given the results of a systematic investigation of some of the extraneous effects associated with the method of measurement.The tests were made under carefully controlled conditions with the test cell incorporated in a closed distillation system. Among the factors influencing the electric strength of pure liquids, the effects of moisture and gas in the liquid, as well as of gas adsorbed on the electrode surface, were examined. It was found that, for pure liquids, the conditioning of electrodes, i.e. the gradual increase of the electric strength with successive voltage applications, appears to be due to a gradual degassing of the electrodes. No such effect was observed with artificially degassed electrodes.Experiments on the effect of the electrode geometry have shown the remarkable result that, using a test cell of sufficient diameter, the electric strength of pure liquids does not depend on the size of the electrodes and their spacing, except for very small spacings, where there appears to be a tendency for the electric strength to increase.