Perceptual learning was examined with respect to variations in ECT electrode placement (bilateral versus right unilateral) and ECT stimulus waveform (sinusoidal versus brief-pulse). While patients receiving right unilateral ECT demonstrated more perceptual learning than did those receiving bilateral ECT, no difference in perceptual learning resulted from the variation in electrical stimulus waveform. Furthermore, the amount of perceptual learning was unaffected by EEG seizure duration and by the total amount of electrical stimulus energy delivered. The theoretical issue of whether an electrical or a seizure difference between bilateral and right unilateral ECT is responsible for inter-group learning or memory differences is discussed, as well as practical issues related to the choice of electrode placement.