To estimate a diagnostic value of antibodies to cyclic citrullinized peptide (CCP) in rheumatoid arthritis (RA).The study was made of 85 RA patients. Of them, 48 patients had early RA, i.e. of 8 month and less duration. The control group consisted of 35 patients with non-differentiated arthritis (NDA) and 8 healthy donors. Concentrations of CCP antibodies, rheumatoid factor (RF) IgM and RF IgA were measured with enzyme immunoassay (EIA).The level of CCP antibodies in RA patients (76.3 +/- 43.8; median 100.0 U/ml) was significantly higher than in NDA patients (25.1 +/- 43.9; median 0.8 U/ml; p < 0.05) or in donors (0.38 +/- 0.36; median 0.2 U/ml; p < 0.05). A correlation was found between the CCP antibodies level and that of RF IgM (chi2 = 15.4; p = 0.001) and RF IgA (chi2 = 10.3; p = 0.001). Sensitivity (82%) and specificity (90%) of CCP antibodies in RA diagnosis was higher than these parameters for RF IgM and IgA (78%, 86% and 72%, 83%, respectively). Simultaneous tests for CCP antibodies, RF IgM and RF IgA led to a 93% specificity. CCP antibodies were detected in 50% patients seronegative by RF IgM and in 62% patients seronegative by IgA. Detection of CCP antibodies was closely associated with early RA (chi2 = 30.8; p = 0.0001).The EIA for CCP antibodies is a sensitive and specific serological test for early RA diagnosis.