Octreotide reduces perception of rectal distension in normal volunteers and irritable bowel patients. To localize octreotide's site of action, perceptual and evoked potential responses to rectal electrical stimulation were tested in seven normal volunteers after double-blind octreotide (100 micrograms 2) or placebo. After octreotide, the currents needed to elicit threshold perception of square-wave impulses delivered to the rectum were 29% higher than after placebo. When electrical stimulation was delivered at constant currents 50% above threshold, rectal perception scores were significantly reduced after octreotide compared with placebo. Rectal electrical stimulation led to characteristic and reproducible cerebral evoked potentials. Octreotide had no effect on latencies, but reduced peak-to-peak amplitudes by 35% compared with placebo. Rectal electrical stimulation also led to characteristic and reproducible spinal evoked potentials. Octreotide had no effect on spinal latencies, but reduced peak-to-peak amplitudes by 51%. In conclusion, octreotide reduces perception of rectal electrical stimulation, which is associated with inhibition of cerebral and spinal evoked potential amplitude, indicating effects on spinal afferent pathways.