From an epidemiological point of view, left-sided diverticulosis represents a civilizational disease of Western countries. It occurs rarely during childhood and frequently in later years. A diet high in fat and meat, low in vegetables, and with insufficient fiber content apparently encourages its genesis. Physical activity seems to counteract diverticulosis while alcohol consumption, smoking, and caffeine ingestion have no effect. The extent of diverticulosis is not commensurate with the extent of complaints. Only a few patients with diverticula develop diverticulitis. Pathogenetically, several factors play a role in the development of diverticulosis. Elevated intraluminal pressure as well as acquired structural changes of the intestinal wall seem to be decisive factors, which intensify with increasing age. These changes are caused by ultrastructural alterations of the muscle and connective tissue related to collagen and elastin metabolism, which presumably can be genetically determined. Intestinal disturbances of innervation and motility also contribute to the formation of diverticula. The term "hypersegmentation" is an attempt to combine these factors into a single pathogenetic model.