Diverticular disease comprises a spectrum of illness beginning with the irritable bowel syndrome and progressing to the life-threatening complications of diverticulitis and hemorrhage. Step-wise progression of this disease may be seen but is not invariably present; many patients with diverticulosis do not have preceding symptoms of the irritable bowel syndrome. The typical complaints of irregularity of bowel habits and abdominal pain will usually respond to the relatively new treatment modality of a high fiber diet with added wheat bran. Barium enema x-ray examination remains the primary diagnostic modality in the investigation of diverticular disease, and colonoscopy should be used only in the presence of certain specific circumstances. Surgery, aimed at the treatment of complications of this disease, has progressed to the point where one-stage extirpation of the diseased bowel is recommended.