In general, the colonic mucosa is macroscopically normal in collagenous colitis, although minor, non-specific abnormalities may be found. Significant endoscopic abnormalities, "mucosal tears" representing longitudinal mucosal lacerations, have been reported in a few patients with collagenous colitis. We report the cases of three women with collagenous colitis and mucosal tears detected at the index colonoscopy in order to illustrate the endoscopic characteristics and review the literature. Including the present cases, a total of 12 patients with mucosal tears and collagenous colitis have been reported. In 10 patients, the mucosal lacerations involved the ascending or the transverse colon. Three of the 12 patients had a colonic perforation immediately after the colonoscopy. The colonoscopist should be aware that the risk of perforation is likely to be increased when mucosal tears are present.