Background: The natural history of acute diverticulitis remains unclear, with the role of prophylactic surgery following conservatively managed diverticulitis increasingly controversial. This study investigated recurrence rates, patterns and complications after conservatively managed diverticulitis. Methods: This was a retrospective chart review of all patients admitted with diverticulitis between June 1997 and June 2002. Demographic data, management, recurrence rates, complications and subsequent surgery were recorded. Results: Some 502 patients were identified, 337 with uncomplicated and 165 with complicated diverticulitis. Median follow-up was 101 (range 60-124) months. Of 320 patients with uncomplicated diverticulitis managed conservatively, 60 (18.8 per cent) had one episode of recurrence, whereas 15 (4.7 per cent) had two or more episodes. After an initial attack of uncomplicated diverticulitis, only 5.0 per cent developed complicated disease. Complicated disease recurred in 24 per cent, compared with a recurrence rate of 23.4 per cent in those with uncomplicated diverticulitis (P = 0.622). When recurrence occurred, it usually did so within 12 months of the initial episode. Conclusion: Acute diverticulitis has a low recurrence rate and rarely progresses to complications. Any recurrence is usually early, in a pattern more consistent with failure of the index episode to settle. Subsequent elective surgery to prevent recurrence and the development of complications should be used sparingly.