Familial Mediterranean fever (FMF) is an autosomal recessive disease which predominantly affects certain ethnic groups mainly Sephardic Jews, Turks, Arabs, and Armenians. Differential diagnosis of an attack of FMF with appendicitis could be difficult in patients presenting with acute abdomen. Circulating levels of resistin and visfatin have been shown to increase in several inflammatory conditions. In this study we aimed to investigate the role of resistin and visfatin in diseases activity by monitoring these adipokines' levels in patients with FMF (attacks and attack-free period) and acute appendicitis. The study involves four groups: group 1-31 FMF patients at attack (M/F, 14/17), group 2-27 FMF patients at attack-free period (M/F, 9/18), group 3-29 acute appendicitis patients (M/F, 16/13), and group 4-20 healthy controls (M/F, 10/10). Erythrocyte sedimentation rate, C-reactive protein, white blood cell count, fibrinogen, resistin, visfatin, interleukin-1β, interleukin-6, interleukin-10, TNF-α, and IFN-γ were evaluated concurrently. Resistin level could be a useful test in diagnosis of FMF patients in attacks period but not in acute appendicitis as differential diagnosis. Measuring visfatin levels would not give additional information neither for attacks and attack-free period nor FMF attack and appendicitis. © 2011 Clinical Rheumatology.