BACKGROUND: Laparoscopic appendectomy is the commonest emergency abdominal surgery performed worldwide. Despite the benefits associated with its minimally invasive nature, conversion to open appendectomy is sometimes inevitable. Understanding the risk factors for conversion is invaluable in optimising patient counselling and intra-operative decision making.METHOD: Medical records of 1117 consecutive adult patients undergoing appendectomy for suspected acute appendicitis between January 2002 and December 2007 were retrieved for the study. Some 369 patients receiving open, interval, and incidental appendectomy were excluded, while the peri-operative variables of the remaining 748 patients were evaluated for prediction of conversion.RESULT: Laparoscopic appendectomy was successful in 594 patients (79.4%), but conversion was required in 154 patients (20.6%). Reasons for conversion included technical difficulty (46.9%), significant peritoneal contamination (23.4%), uncertain pathology (15.5%), unhealthy appendiceal stump (11.7%), and technical complications (2.5%). In multivariate analysis, conversion was independent of gender, body weight, ASA class, previous abdominal surgery, atypical site of pain, presence of peritonism, hypotension, tachycardia, leukocytosis, timing of operation, delay in operation, and experience of surgeon. Only [1] age ≥60 years (p<0.0001, OR=3.10, 95% C.I.=1.99-4.82), [2] duration of pain ≥4 days (p<0.0001, OR=3.38, 95% C.I.=2.05-5.56), and [3] fever >38 degrees Celsius (p=0.033, OR=1.55, 95%C.I.=1.03-2.32) were independent factors predicting conversion. In addition, patients requiring conversion had significantly worse clinical outcomes when compared to those with successful laparoscopic appendectomy. These included increased operative time (100mins vs 70mins, P<0.0001), prolonged hospital stay (8d vs 5d, P<0.0001), higher wound infection rate (8.4% vs 4.0%, P=0.025), and more intra-abdominal collections (9.7% vs 3.9%, P=0.003).CONCLUSION: Elderly age, prolonged presentation and high fever were independent factors predicting conversion from laparoscopic to open appendectomy for acute appendicitis.