Reumathoid arthritis (RA) is one of the most common autoimmune diseases (1-2% European population). The most significant clinical symptom is an inflammation of the synovial membranes which causes a painful swelling of the articulations and the ankylosis. In order to correctly diagnose RA it is necessary to exclude other forms of arthritis: in such a diagnostic process, the laboratory plays an important role in the determination of Rheumatoid Factor (RF) antibodies of class IgM, detectable in 60-80% of the patients with RA. The RF antibodies are sensitive but not very specific markers; on the contrary, anti-CCPs are characterized by a specificity of over 90% in patients affected by RA ,and are detectable in a very early asymptomatic stage in the approximately 70% of RA patients whereas only 2% of the control subjects resulted positive. Therefore, the presence of Anti-CCP antibodies can be used in the diagnosis of RA, particularly in the case of erosive arthritis, in childhood in the case of juvenile RA. The test also appears, to be useful in differentiating the collagen pathologies with concomitant arthritis from the RA. The Anti-CCP antibodies test has an important prognostic value in the monitoring of articular radiologically detectable damage. The kit’s quantitative determination is useful in the control and verification of the effects of pharmacological therapy. The Anti-CCP antibody test, together with the determination of RF, increases the ratio of sensitivity / specificity. 20% of the RAs are RF-negative and 15/20% of the RAs are positive only to RF. The simultaneous positive result of a sample to RF and CCP has a positive predictive value of about 100%. The levels of anti-CCP antibodies are not necessarily correlated to the evolutionary stage of the illness. The advantage of the anti-CCP antibodies is that they are detectable in the patient sera up to 10 years prior to the appearance of symptoms. In addition, in cases of early arthritis a positive test result, according to some studies is related to the development of bone erosive lesions of the articulations.