Acute colonic pseudo-obstruction is a functional disorder that closely mimics mechanical large bowel obstruction, and in which inadvertent laparotomy carries a high mortality. Eleven such patients were treated by pharmacological manipulation of the autonomic innervation to the colon with guanethidine and neostigmine. Eight responded to treatment with passage of flatus and/or stool within 10 min with complete resolution of symptoms. In three patients the treatment failed. Postural hypotension occurred in only one patient and no other serious side-effect was apparent. This pharmacological approach to the management of acute colonic pseudo-obstruction is suggested as an alternative to the other treatment options of colonoscopic decompression or surgery, when conservative management has failed.