Electron transport by the human neutrophil NADPH oxidase is an important microbicidal weapon for phagocytes. The electron current (I e ) generated by the neutrophil NADPH oxidase is poorly characterised due to the lack of appropriate electrophysiological data. In this study, I fully characterise the neutrophil generated I e when the NADPH oxidase is activated by NADPH and GTPγS. The neutrophil I e was markedly voltage-dependent in the entire voltage range in comparison to those electron currents measured after chloride was removed from the external bath solution. The difference in I e measured in chloride free conditions was not due to a change in the activation kinetics of voltage-gated proton channels. The I e depolarises the neutrophil plasma membrane at a rate of 2.3Vs −1 and this depolarisation was opposed when voltage-gated proton channels are activated. 3mM ZnCl 2 depolarised the membrane potential to +97.8±2.5mV (n=4), and this depolarisation was abolished after NADPH oxidase inhibition.