The surgeon is frequently confronted with the problem of how much colon to resect when operating on patients with colonic diverticulosis or diverticulitis. Two questions arise: will diverticulosis progress in the proximal colon if only the sigmoid is removed, and will diverticulitis recur in the more proximal diverticula? To evaluate these potential problems, the histories were reviewed of 61 patients who had elective sigmoid resection for diverticular disease and who had barium enema examinations before operation, early during the postoperative period, and at least five years later. Progression of diverticulosis was noted in only nine (14.7 per cent) patients on repeat barium-enema examination five to nine years after resection; the progression was noted to be minimal in all nine. Seven patients (11.4 per cent) had signs and symptoms of recurrent diverticulitis. Only three patients demonstrated progression of diverticulosis and recurrent diverticulitis. We see no benefit in resecting all of the diverticula-bearing colon after adequate sigmoid resection, as there is minimal progression in the diverticular process and the risk of recurrence is low.