THIS is a review of cases of patients with diverticulitis coli admitted to Mount Carmel Hospital in Columbus, Ohio, from 1955 to 1966. The reason for making the study was to determine if a reasonable prognostic yardstick could be developed. There is no disagreement that surgery is indicated for the complications of this disease, but indecision and controversy exist between surgeons and internists regarding the proper advice to give the patient about his future course if he has recently responded to conservative measures. Might it be possible to advise the victims of this disease as to its possible recurrence, time of recurrence, and chronicity, and to tell whether an elective surgical procedure is ever indicated? Material There were 374 patients admitted to Mount Carmel Hospital, over an 11-year period from 1955 to 1966, with the diagnosis of diverticulitis of the colon. There were 218 women (58%) and 156 men (42%).