The prevalence of diverticulosis in western countries has increased and two-thirds of the population over the age of 85 are now affected. Diverticulitis results from inflammation and subsequent perforation of a colonic diverticulum. Mild forms of diverticulitis usually present with gradually increasing symptoms from the lower left quadrant of the abdomen, whereas acute complicated disease is characterised by dramatic onset of abdominal pain, followed by fever within a few hours. The standard treatment for uncomplicated diverticulitis is bowel rest, with liquid diet or intravenous fluids in combination with antibiotics. Patients not responding to conservative treatment within the first 24 hours require further evaluation by computed tomography or ultrasonography. If an abscess is present, it can often be drained percutaneously. In cases of perforation and peritonitis, surgical intervention is mandatory, though no consensus exists as to the choice of procedure. Fistula formation and intestinal obstruction are also indications for surgical intervention, although the frequent recurrent attacks which commonly afflict these patients are seldom associated with severe complications. Prophylactic resection is not to be recommended for patients with diverticular disease, but a high-fibre diet may afford protection by preventing further complications.