Colonoscopies are performed in the primary care in growing numbers, also by general practitioners. In diagnosing adenomas and cancers, colonoscopy is preferable to sigmoidoscopy. Colonoscopy should be performed as the initial investigation when looking for possible colonic causes of iron deficiency anaemia or occult blood in the faeces. Thorough investigation of these patients and endoscopic follow-up of adenoma patients is the key to an early diagnosis and treatment as well as prevention of colon cancer. Readiness for polypectomy is desirable, at least if colonoscopy is performed because of positive screening test for faecal occult blood. Sigmoidoscopy is often sufficient in the investigation of bloody or prolonged diarrhoea or fresh blood from the anus if the cause of the bleeding becomes evident in the investigation. Microscopic colitis can almost always be diagnosed from the sigma. If an adenoma is detected in sigmoidoscopy, colonoscopy must always be performed. Fiberosigmoidoscopy should replace rectoscopy with a stiff instrument whenever sigmoidoscopy is available. Sigmoidoscopy must always be complemented by proctoscopy and touch per rectum in order to detect abnormalities of the anal canal.