Ulcerative colitis (UC) is an inflammatory disease of the colonic mucosa. The presence of gene responsible for FMF, MEFV, which frequently causes inflammation, may aggravate the clinical course of UC. We aimed to determine the prevalence of MEFV mutations in UC patients and its impact on the clinical course. Four groups were formed as group 1 UC with distal disease, group 2 UC with pancolonic disease, group 3 UC with total colectomy, and group 4 Rheumatoid Arthritis (RA) patients. Eleven mutations of FMF gene were investigated. The mean age of group 1, 2, 3, and 4 were 46.7 +/- A 13.9, 43.8 +/- A 12.9, 44.8 +/- A 14.2, and 45.8 +/- A 10.9 years, respectively. The mutations were identified in 19 of the 54 UC patients (35.2%). Homozygous E148Q in 2 patients (3.7%) and heterozygous in 17 patients (31.5%) (E148Q 11.1%, M694V 5.6%, V726A 5.6%, K695R 1.8%, M680I 1.8%, and compound heterozygous 5.6%) were determined. Frequencies of MEFV mutations in group 1, 2, and 3 were 30, 27.3, and 58.3%, respectively. The mutations were identified in 3 of the 20 RA patients (15%). All of them were heterozygous. The rate of MEFV mutations were higher in group 3 than in group 4 (P = 0.018), and the number of attacks that were treated with steroid in all UC patients with mutation positive was higher than in mutation negative (P = 0.016). FMF gene mutations may be identified in UC patients up to 58.3%. It may be suggested that the UC patients with severe form should be identified for MEFV mutations before the judgment of colectomy.