Introduction: Acute appendicitis in the elderly commonly presents at a more advanced stage as manifested by higher incidences of perforation and sepsis. The factors responsible for this delayed presentation are not clearly elucidated. This study was conducted to ascertain what factors may account for this phenomenon. Methods: A five-year retrospective chart review from 1999-2004 was conducted at a tertiary referral center in which 375 consecutive records were identified for appendectomy. After excluding incidental, interval or pathologically negative appendectomies, 276 patients were identified and stratified into two groups: patients 60 years old or less (243 patients) and patients 70 years old or greater (33 patients). Clinical parameters studied included the Alvarado criteria (RLQ pain, pain migration, anorexia, nausea/vomiting, rebound pain, fever, leukocytosis, left shift), interval from symptom onset to ED presentation, interval from ED presentation to surgery, length of hospital stay (LOS), laboratory profile, CT findings, operative procedure and findings, pathology, and postoperative complications. T-test and Chi square were used for statistical comparisons.Results: Time from symptom onset to ED presentation was significantly longer in the elderly (66.1 hrs vs. 41.8 hrs, p<0.045) but time from triage to surgery was not (13.3 hrs vs. 13.6 hrs, p=0.94). The elderly had significantly decreased pain migration to the RLQ (27% vs. 60%), decreased nausea/vomiting (64% vs. 81%) and anorexia (45% vs. 65%); however, rates of localized tenderness were the same (100% vs. 94%). There was no difference in WBC elevation (79% vs. 78%, p=0.45) between the two groups, but the elderly more commonly had a left shift (96% vs. 80%). Older patients had a significantly higher rate of suppurative (72% vs. 49%, p<0.023) and perforated appendicitis (73% vs. 25%, p<0.001) and a significantly longer LOS (7.3 hrs vs. 3.6 days, p<0.001). They were more likely to have open rather than laparoscopic appendectomy (82% vs. 60%, p<0.02). Overall complication rates were higher in the older group (36% vs. 20%).Conclusion: Factors which appear to be associated with the advanced disease state of appendicitis in the elderly include delay in coming into the ED as well as more subtle and atypical pain presentation. Reasons for delayed ED presentation are unclear but may be related to blunting of abdominal pain in the elderly, the diffuse nature of their pain, a poor family support system, and/or poor body awareness. Shortening the pre-ED admission interval appears to be the most important factor in lowering the higher perforation and complication rate in elderly appendicitis.