Abstract: The only diagnostic test that currently exists for Behcet’s disease (BD) is the pathergy test. A positive pathergy test (PPT) is an important component of many of the 16 sets of classification/diagnosis criteria used to diagnose BD. The aim of this study was to determine the importance of a PTT in the performance of the diagnosis/ classification criteria for BD. Patients and methods All patients listed in the BD registry of the Rheumatology Research Center, Tehran (6,727) and 4,648 BD controls were enrolled in the study. The diagnosis was clinical when no other diagnosis could explain the patient’s manifestations. The criteria were tested with and without PPT results. Sensitivity, specificity, and accuracy were calculated. Results Without PPT, all sets of criteria lost sensitivity, gained specificity, and lost accuracy, with the exception of the Cheng–Zhang criteria. The largest loss in sensitivity was for the Hubault–Hamza (35 %) and Dilsen (17.3 %) criteria; the least was for the Curth (1.9 %) and ICBD (6.5 %) criteria. The largest gain on specificity was for the Dilsen (4.7 %) and Curth (3.1 %) criteria; the least was for the Japan (0.1 %) and Japan revised (0.1 %) criteria. The greatest loss in accuracy was for the Hubault–Hamza (20.4 %) and Dilsen revised (9.3 %) criteria; the least was for the ICBD (3.6 %), while Curth gained 0.3 %. Conclusion Without PPT as a criterion for the diagnosis of BD, the sensitivity and accuracy of the sets of classification/ diagnosis criteria decrease, while the specificity improves. Keywords Behcet’s disease  Diagnosis  Criteria for diagnosis  Vasculitides