In this study, our aim was to investigate the prevalence of Mediterranean fever (MEFV) gene mutations in patients with ankylosing spondylitis (AS) and assessing their clinical significance. Ninety-five consecutive patients (12 women, 83 men) with active AS were included to the study. All patient's relevant clinical data were recorded at the beginning and patient assessment measures were performed. The frequency of the eight most common MEFV mutations: M694V, V726A, E148Q, M680I, M694I, P369S, F479L, and the R761H were determined. Genetic analysis was carried out by the NanoChip Molecular Genetics Workstation. NSAIDs were given to patients for treatment. The rate of MEFV mutations and their clinical significance were assessed. With regard to the MEFV mutation analysis, 30.5% of AS patients were found to have at least one mutation. The response rate to the NSAIDs (P=0.825) or frequency of patients having active disease (P=0.066) after the treatment, were not found different between the patients those have MEFV mutations and the patients those were non-carriers. Furthermore, no clinical and laboratory difference between MEFV mutation carriers and non-carriers were found. We think that although prevalence of MEFV mutations is significantly high in AS patients without clinical features of familial Mediterranean fever, its influence to the prognosis is less likely. Further investigations are needed to define the impact of MEFV mutations on the disease course of ankylosing spondylitis.