Objectives: Define the role of CRP in acute appendicitis diagnosis, the cut-off concentration to diagnose and the corresponding value, examine the correlation between serum CRP concentration and inflamed appendix condition as well as between clinical symptoms, blood tests and appendicitis diagnosis. Methods: Paired case-control study, carried out in Cho Ray Hospital and Gia Dinh People's Hospital, from 11 - 2008 to 3 - 2009.Results: Diseased group includes 126 patients (101 appendicitis, 25 non-appendicitis), evidenced group includes 101 healthy adult people.