Colonic smooth muscle spike potentials and contractility were recorded during the periods of stress by a bipolar electrode-perfused catheter apparatus placed in the rectosigmoid colon. Healthy subjects and patients with the irritable colon syndrome (ICS) were exposed to three standardized stressful conditions: (1) ice-water immersion, (2) Stroop stimulus differentiation test, and (3) ball sorting. In healthy controls, colonic motility. An increase in colonic motility occurred in patients with the irritable colon <0.5), or="" ball="" sorting.="" respiratory="" frequency="" also="" increased="" after="" exposure="" to="" the="" stressful="" stimuli.="" however,="" repeat="" exposures="" to="" the="" stress="" tests="" did="" not="" stimulate="" colonic="" motility.="" an="" increase="" in="" colonic="" motility="" occurred="" in="" patients="" with="" the="" irritable="" colon="" syndrome="" pretreated="" with="" a="" placebo="" after="" exposure="" to="" ice="" water="">P<0.05), stroop="" test,="" or="" ball="" sorting="">P<0.05). however,="" after="" exposure="" to="" the="" stressful="" situations="" patients="" pretreated="" with="" chlordiazepoxide="" had="" a="" diminished="" increase="" in="" colonic="" motility="" or="" in="" respiratory="" frequency.="" these="" studies="" suggest:="" (1)="" in="" healthy="" controls="" habituation="" reduces="" the="" stress-related="" increase="" in="" colonic="" motility,="" and="" (2)="" in="" patients="" with="" the="" irritable="" colon="" syndrome,="" chlordiazepoxide="" decreases="" the="" stress-related="" increase="" in="" colonic="">