The International Study Group (ISG) for Behqet's disease proposed new international criteria for Behçet's disease in 1990. The aim of this study was to assess the performance of these criteria in new patient groups Sensitivity was determined in 300 patients with Behçet's disease from seven countries, and specificity in a group of 62 control patients from China. The ISG criteria performed well compared to the other criteria sets in current use.