The present study evaluated the ability of a weak electrical prepulse to modify startle caused by a more intense shock. Painful electrical shocks (150 V, 0.5 ms duration) were presented to the upper arm of college student participants, preceded on some trials by a weaker shock (0.5 ms duration, at perceptual threshold) at the same location. Intense shocks elicited eyeblink reflexes, and these eyeblinks were inhibited by weak electrical prepulses. These data suggest that the inclusion of prepulses immediately preceding painful therapeutic shocks, such as those generated by an implanted cardioverter-defibrillator, might be capable of reducing the startle response generated by that therapeutic shock.