BACKGROUND: Colonic diverticulitis in the young has been considered to have a virulent course, high morbidity, and high operative rate. As a result, elective resection of the involved colonic segment after the first clinical episode has been the usual practice. PURPOSE: This study presents our experience with acute diverticulitis in the young. METHODS: In the last nine years, 63 patients younger than 45 years were treated for acute diverticulitis at our institution. A retrospective review was performed to determine the clinical course and outcome of these patients. RESULTS: Clinical presentations, radiographic tests, operative findings, and pathology results revealed that 57 patients had a pericolonic contained disease (Hinchey Stage I). Two patients had a large pelvic abscess (Hinchey Stage II), and four patients had a diffuse peritonitis (Hinchey Stage III). Forty-one patients (65 percent) were successfully treated medically with antibiotics and bowel rest. Of 22 patients (35 percent) who underwent emergent operations, 12 patients' diseases had been erroneously diagnosed preoperatively (9 ''appendicitis''). CONCLUSION: Diverticulitis at a young age does not have a specific aggressive nature. Although, it is associated with a high rate of emergency operations, many of these are performed for a mistaken diagnosis. The recommendation for routine elective resection following the first episode of diverticulitis should be reassessed.