The treatment of ulcerative colitis remains empirical because of undetermined etiology and pathogenesis and incomplete understanding of the underlying inflammatory and immunological events. Since trapencaine has been repeatedly demonstrated to protect the gastric mucosa from the injurious effects of a variety of noxious stimuli, its efficacy against acute inflammatory attack of the colonic mucosa was studied in a rat model of colitis.Colitis was induced by intracolonic administration of 4 % acetic acid to anaesthetised rats. Vehicle or trapencaine in doses of 3, 10, and 30 mg/kg/5 ml were given 30 min before acetic acid and the resulting injury was assessed after 48 h. Gross mucosal findings were registered, contractility of colonic muscle strips was examined in vitro and myeloperoxidase activity in colonic mucosal scrapings was determined spectrophotometrically.Trapencaine pretreatment was found to reduce the extent of the inflammatory colonic mucosal injury, attenuate the increased responsiveness of colonic smooth muscle and abolish the increase in myeloperoxidase activity asociated with acute colitis.