Behcet's disease is an inflammatory disease of unknown etiology. Pathergy test is the only diagnostic test for Behcet's disease. The evaluation can be done either clinically and/or histopathologically. In the present study, we compare the sensitivity and specificity of clinical vs. histopathological evaluation of the pathergy test.This was a retrospective study in patients who underwent pathergy tests at Phramongkutklao Hospital, Thailand between January 1, 2011 and December 31, 2013. Fifty-eight cases met the inclusion criteria and were included into the study. All basic demographic data were obtained from the medical records. The sensitivity, specificity, and accuracy of the test were evaluated.There were 33/58 (56.9%) cases with the final diagnosis as Behcet's disease. The sensitivity, specificity, and accuracy of the clinical evaluation of pathergy test were 30.3%, 64%, and 44.8% respectively. Upon using the histopathological evaluation, the sensitivity, specificity, and accuracy were 100%, 16%, and 63.8%, respectively.Our results showed that the histopathological evaluation of pathergy test helped to improve the accuracy and sensitivity, but the specificity was low. We suggest the use of histological evaluation of the pathergy test in cases where Behcet's disease is highly suspected especially in areas where the disease is uncommon.