Diverticular disease affects upwards of 50% of the population over the age of 60 years in Western countries and is becoming more common as the population ages. Studies from the 1970s and 1980s related its occurrence to the use of low-fiber diets and to the prolonged colonic transit time and increased intraluminal pressure associated with low-volume stools. Pulsion diverticula (pseudodiverticula) emerge through the thickened circular layer of the muscularis propria of the left colon at points of penetration of the vasa recta that supply the submucosa and mucosa. Complications of diverticular disease such as hemorrhage, diverticulitis, peridiverticular abscess, fistula, and perforation are well recognized. More recently, attention has been drawn to the polypoid prolapsing mucosal folds that may develop as the affected segment of bowel (usually the sigmoid) becomes shorter and to changes in the mucosa surrounding the diverticula and in the bowel wall that may result in confusion with ulcerative colitis or Crohn disease (sigmoid colitis-associated diverticulosis [SCAD]). Distinguishing SCAD from these entities is extremely important, and pathologists should be aware of the possibility of overdiagnosing chronic inflammatory bowel disease in biopsies or resection specimens of sigmoid colon with diverticular disease.