Diverticulosis, which is an acquired condition marked by mucosal herniation through defects in the colonic wall, has been termed both a "disease of the 20th century" and a "disease of Western civilization" due to its increasing prevalence in modern times and its striking geographical variability. Both of these epidemiological observations may provide interesting insights into the pathophysiology of diverticulosis. This chapter will review the known epidemiology of diverticulosis coli and its main complications: diverticulitis and diverticular haemorrhage. Where possible, attempts will be made to place these observational reports in the context of both the cause and clinical behaviour of this disorder.