There is strong evidence that the determination of autoantibodies against filaggrine is a very useful tool for the diagnosis of rheumatoid arthritis (RA). Anti-cyclic citrullinated peptide antibodies (Anti-CCP)-ELISA appear to be the most efficient test among those available for the detection of antifilaggrine autoantibodies, as it has the best diagnostic accuracy for the diagnosis of RA. Furthermore, the anti-CCP-ELISA determination in early arthritis is a good predictor of disease persistence and radiographic joint damage. The positivity of Anti-CCP some years before the onset of the RA and the high concentration of autoantibodies in synovial fluid suggest a possible pathogenetic role of citrullination. However, at present, it is unclear whether anti-CCP antibodies have a better diagnostic performance than rheumatoid factor in recent onset synovitis and if they confer any additional value to the prognostic evaluation obtained with validated predictors of outcome (FR, joint count, duration of disease).