This study aimed to measure serum active IL-18 levels in patients with AOSD and evaluate their clinical and diagnostic significance.<h4>Methods</h4>Serum samples were obtained from 47 untreated patients with AOSD, 42 patients with rheumatoid arthritis (RA), 9 patients with familial Mediterranean fever (FMF), and 26 healthy controls (HCs). Here, IL18 is linked to adult-onset Still disease.