Introduction: Acute appendicitis is one of the most common abdominal emergencies. The clinical diagnosis is often difficult even for experienced surgeons, however, as evidenced by the high rate of negative explorations. A delay in diagnosis of acute appendicitis is associated with increased risk of perforation and further complications. The aim of the present study was to assess the preoperative YKL-40 levels on for a clinical suspicion of acute appendicitis. Methods: Between August 2008 and December 2008, a total of 34 patients who underwent appendectomy with a clinical diagnosis of acute appendicitis were studied. Patients underwent appendectomy with the preoperative diagnosis of acute appendicitis. The appendix specimens were classified as normal appendix (group 1; 10 patients), acute appendicitis (group 2; 24 patients). Serum YKL-40 levels were determined by a commercial ELISA. Results:The levels of serum YKL-40 were significantly higher in the group 2 compared with the group 1 (66.4 ± 13.2 vs 41.6 ± 11.6 ng/mL, p < 0.001). Receiver operating characteristic curves of YKL-40 levels counts was on a statistically significant level (area under the curve [AUC] = 0.926, p < 0.001) Conclusion: YKL-40 may be a useful marker for diagnosis of acute appendicitis but the number of subjects was limited in this study, future studies are required to confirm the results presented here.