The effects of cholinergic stimulation on the entire human colon are at present relatively unknown. For this reason, we evaluated the influence of a short-lived anticholinesterase agent, edrophonium chloride, on proximal and distal colonic contractile activity in man. Eight healthy volunteers of both sexes were studied with a multi-lumen manometric probe positioned with the aid of a colonoscope. Recordings were then obtained 30 minutes pre- and post-drug administration. Edrophonium chloride (10 mg intravenous) significantly stimulated both proximal and distal colonic contractile activity, and the maximum increase was observed within 10 minutes following injection, although some differences were observed between colonic segments in response to the drug. No important side effects were complained of after edrophonium. Due to the potent stimulatory property on colonic smooth muscle, to its short duration of action, and to the paucity of side effects, it is concluded that edrophonium chloride may be useful as a stimulating substance during manometric investigations of the human colon.