Quantitative studies of the afferent pathways from hollow viscera have been limited by the lack of an easily controlled, reproducible visceral stimulus. We adapted a slow distention device to allow for rapid distention to study the afferent pathways from the rectum. The device produced a pressure increase of 10 mm Hg in 42 msec and of 20 mm Hg in 60 msec. We recorded cerebral evoked potentials (EPs) after rectal balloon distention in 17 healthy subjects. Several averages of 25 to 50 rectal distentions at 0.17-Hz frequency were recorded. The responses consisted of multiple peaks within 200 msec after stimulation. The mean latency of the initial positive peak was 44 msec, suggesting that a myelinated pathway was stimulated with mechanical rectal distention. Our device produced reliable and repeatable EPs that were independent of balloon characteristics or rectal pressures. EP recording after rectal stimulation may become a useful technique for the physiologic investigation of disorders such as fecal incontinence, constipation, irritable bowel syndrome, and chronic intestinal pseudo-obstruction.