The authors reviewed their experience with diagnosis and treatment of lower gastrointestinal bleeding secondary to colonic arteriovenous malformations (AVM). A diagnosis was established exclusively by endoscopy in 80 percent of the patients. Twenty-eight patients were treated by endoscopic coagulation; bleeding stopped after one or more treatments in 67.9 percent of these patients. There were no complications or mortality as a consequence of endoscopic treatment. Surgery controlled the recurrent bleeding in six of seven cases of failed endoscopic coagulation, and in 13 of 17 cases where surgery only was undertaken, for an overall success rate 79.2 percent. It is concluded that colonoscopy can accurately establish the diagnosis of colonic AVMs in chronic lower gastrointestinal bleeding. Endoscopic coagulation is a useful adjunct in the treatment of this condition, and is safe, effective, and leaves other options open.