BACKGROUND Colonic diverticulosis is the most common incidental lesion found on routine colonoscopy. However, its true natural history is unclear. The aim of this review is to examine the epidemiology of colonic diverticulosis and the incidence of complications, namely acute diverticulitis and diverticular hemorrhage. CONCLUSIONS Many studies have evaluated the epidemiology and risk factors of diverticulosis. Despite the common nature of this entity, little is known about the risk of complications in asymptomatic individuals. It has been suggested that the lifetime risk of acute diverticulitis is 10-25% and that of diverticular hemorrhage is 3-5%. These risk estimates were based on older literature without accurate studies on true prevalence. Three recent retrospective observational cohort studies including subjects identified at colonoscopy have addressed this issue, providing information on the long-term risk of complications of colonic diverticulosis. Cumulative data from these studies support an incidence of acute diverticulitis of 1.5-6.0 per 1,000 patient-years and 0.46 per 1,000 patient-years for diverticular hemorrhage. CONCLUSIONS Diverticulosis is a very common condition in individuals > 50 years of age. Based on population-based colonoscopy studies, the natural history of colonic diverticulosis appears favorable with a far lower incidence of complications than previously thought.