Objective: This study aimed to investigate the frequency in which familial Mediterranean fever (FMF) coexists with other diseases and determine whether Mediterranean fever (MEFV) gene mutations are involved in such coexistence. Material and Methods: In total, 142 consecutive patients with FMF investigated for MEFV mutation were enrolled in this study [Female: 87; Male: 55, mean age 32+/-12 years (11-62)]. All the patients were questioned for the presence of concurrent disorders, and the medical records of these patients were revised retrospectively. A previous diagnosis of inflammatory disorder other than FMF was considered true if it met the relevant criteria. MEFV mutations were divided into 2 groups, namely M694V and its subgroup (homozygous or heterozygous) (Group I) and others (Group II). Compound heterozygosity for M694V mutation was included in Group II to form a homogeneous group for Group I. Group I and Group II were compared according to phenotypical features. The presence of MEFV mutation was investigated in exons 2, 3, 5, and 10 by the multiplex-PCR reverse hybridization method. Results: Concomitant disorders were found in 17 of 73 patients with FMF (23%) in Group I and 5 of 56 patients (8.9%) in Group II (p=0.04). Concomitant disorders in Group I were as follows: 7 cases of amyloidosis, 2 cases of Behcet's disease (BD), 4 cases of ankylosing spondylitis (AS), 1 case of antiphospholipid syndrome, 1 case of Henoch-Schonlein purpura (HSP), 1 case of combination of psoriatic arthritis, HSP, and membranoproliferative glomerulonephritis, and 1 case of AS and amyloidosis. In Group II, the following disorders were found: 1 case of amyloidosis, 1 case of BD, 1 case of AS, 1 case of ulcerative colitis, and 1 case of vitiligo. Conclusion: The presence of M694V mutation may predispose patients with FMF to developing other inflammatory disorders.