The longitudinal musculature of the taenia of the colon does play an important role in diverticular disease (DD), as can be found by comparing light and electron microscopic pictures of the colon from healthy persons and patients with diverticulitis and ulcerative colitis. Already in the early stages histological changes can be found, which have to be interpreted as being due to maximal contraction of the longitudinal musculature and to increased metabolism. These morphological changes are accompanied by increased electrical and mechanical activity. Disturbed function seems to be myogenic, as could be shown by studies with different drugs. These results seem to indicate that it might be preferable to incise the longitudinal musculature of the colon transversally during surgery because of diverticulosis.