&NA;During the last few years, new forms of bowel preparation before surgery and operative endoscopy have been introduced as whole gut irrigation with saline or mannitol solutions. The use of 10 to 20 per cent mannitol solution is, however, likely to alter the composition and quantity of the colonic gases (methane and hydrogen) and to produce explosive mixtures. Some cases of fatal explosions occurring during endoscopic electroresection have been reported. The authors examine the whole gut lavage methods and report a case of colonic explosion during a left hemicolectomy on a patient prepared with 20 per cent mannitol solution.