Eighteen totally deaf human cochleae were stimulated with biphasic square pulses of current through transtympanic needle electrodes. The thresholds of the 2 polarity orders, + - and - +, were compared for various pulse durations. For a pulse duration of 500 microseconds the polarity order - + had the lower threshold. For pulse durations of 2 ms and longer, the polarity order + - had the lower threshold. A discussion is given of the significance of the results for finding out the site of cochlear nerve excitation by the stimuli.