&NA;Conventionally, acquired diverticular disease of the colon has been regarded as a single entity, so far as complications go. Experience at St. Vincent's Hospital, Melbourne, suggests that there are two kinds of diverticular disease, one with the classic muscle abnormality, chiefly confined to the left colon and characterized by inflammatory and perforative complications and the other without muscle abnormality, but with diverticula throughout the colon, in which bleeding is common, perhaps due to a connective‐tissue abnormality which, on the one hand, allows development of diverticula in the absence of abnormal intraluminal pressure and, on the other, provides inadequate support for vessels in the diverticular wall or for vascular malformations, which are therefore likely to bleed. Clinical evidence from admissions to St. vincent's Hospital suggests that both acute and chronic pain may be either inflammatory or associated with muscle spasm and hypertrophy. Finally, there is some evidence to suggest that perforation may be due often, or usually, to abnormal intraluminal pressures rather than to diverticular inflammation.