The present study aims to investigate whether or not FMF patients display abnormal liver functions during attack periods. About 41 consecutive FMF patients with attacks were enrolled on this study. Bilirubin levels, liver transaminases, erythrocyte sedimentation rate and C-reactive protein (C-RP) levels were determined within the first 72 h after the onset of attacks. This procedure could be performed on only 28 of these 41 FMF patients, 4 weeks after the attack of the patients' had completely disappeared. As for the disease control group, 44 patients were determined to be eligible for the study. Another 31 healthy individuals were also included. Hyperbilirubinemia was determined in 11 of the 41 patients (26.8%) with FMF. The number of FMF patients with hyperbilirubinemia was significantly higher than in DC and HC (P < 0.001, P = 0.03, respectively). Levels of liver transaminases slightly increased in four patients with FMF during the attack and two of these four patients had also mild hyperbilirubinemia. A significant correlation was found between C-RP levels and total and unconjugated bilirubin levels in FMF patients with attack (r = 0.43, P = 0.01; r = 0.40, P = 0.02, respectively). In conclusion, mild hyperbilirubinemia may occur in one-fourth of the patients with FMF during the attack period.