Diagnostic colonoscopy was performed on 270 patients, male and female, between the ages of 8 and 85 years, most of them in those with suspected lesion at x-ray examination of colon. In our series, carcinoma, polyps, inflammatory and diverticular disease were the frequent pathology found. Colonoscopy was an excellent method to complete or to make a proper differential diagnosis between tumoral images at x-ray barium enema and inflammatory bowel disease. In 300 colonoscopies performed, there were not any complications.