Several autoantibodies found in RA are directed to epitopes in citrullinated proteins. One of them is anti modified citrullinated vimentin (Anti-MCV). We tested the value a newly developed ELISA for the detection of antibodies againts a genetically modified citrullinated vimentin (anti-MCV) in comparison with an anti-CCP based ELISA system for the diagnosis of RA. Thirty-five patients with RA (mean age; 42.6 ± 10.87 years, mean disease duration; 9.37 ± 3.98 years) were enrolled in this study. Twenty – five ankylosing spondylitis (mean age; 35.88 ± 6.64 years, mean disease duration; 10.25 ± 4.61 years), and 19 healthy subjects (mean age; 40.26 ± 5.11 years) served as controls. Anti-CCP antibodies and Anti-MCV antibodies were measured using ELISA. In all RA patients, mean anti- CCP level was 69.07 ± 90.43 U/ml and anti-MCV level was 665.77 ± 1040.19 U/ml. In patients with AS, the mean anti-CCP level was 10.7 ± 5.22 U/ml and anti-MCV level was 40.54 ± 20.15 U/ml. In healthy controls, the mean anti-CCP level was 11.11 ± 7.65 U/ml, anti-MCV level was 23.12 ± 12.04 U/ml. In patients with active RA, the mean serum anti-CCP level was 100.54 ± 98.07 U/ml and anti-MCV level was 998.74 ± 1154.93 U/ml. In patients with inactive RA, the mean serum anti-CCP level was 8.77 ± 1.55 U/ml and anti-MCV level was 27.59 ± 23.10 U/ml. According to these results; In patients with RA, the mean serum anti-MCV and anti-CCP levels were significantly high compared to patients with AS and healthy controls (p=0.002, p=0.001, p=0.002, p=0.001 respectively). The mean serum anti-MCV and anti- CCP levels were significantly higher in active patients with RA than in inactive patients with RA patients (p=0.001 and p=0.001 respectively). In inactive patients with RA, the mean serum anti-MCV and anti-CCP levels were similar in patients with AS and patients (p=0.484, p=0.308, p=0.09 and p=0.222 respectively). The mean serum anti-MCV levels were correlated with DAS 28 (r=0.531, p=0.001), VAS score (r=0.332, p=0.01), ESR (r=0.458, p=0.001), serum CRP levels (r=0.568, p=0.01), serum RF levels (r=0.529, p=0.001), swollen joints number (r=0.525, p=0.001) and tender joints number (r=0.638, p=0.001). As a result; measurement of serum anti-MCV levels is useful for diagnosis of RA and combined use of anti-MCV and RF may be more useful prognostic factor than either method alone, RF and anti-CCP.