Objective. To explore the diagnostic value of anti-cyclic citrullinated peptide antibody (anti-CCP) detected by ELISA in patients with rheumatoid arthritis (RA). Methods. The synthesized cyclic citrullinated peptide was used as substrate for ELISA. Anti-CCP antibody was detected by ELISA in 191 patients with RA, 132 with rheumatic diseases other than RA, and 98 with nonrheumatic diseases. The antiperinuclear factor (APF), anti-keratin antibody (AKA), rheumatoid factor (RF), and HLA-DR4 gene complex were also tested in each RA patient. The results of these tests were compared with anti-CCP antibody to examine the correlation between them. Results. Ninety (47.1%) patients with RA, 4 (3.0%) with other rheumatic diseases, and 2 (2.0%) with nonrheumatic diseases were found to be anti-CCP antibody positive by ELISA. The sensitivity of anti-CCP antibody was 47.1%, with a high specificity (97.4%) in RA. Anti-CCP antibody correlated with APF, AKA, RF, and HLA-DR4 gene complex. Conclusion. A new modified anti-CCP antibody test had a moderate sensitivity (47.1%) but a high specificity (97.4%) in patients with RA and was found as a valuable supplement to diagnosis of RA. Anti-CCP correlated with APF, AKA, RF, and HLA-DR4 gene complex, but did not completely overlap with them. Anti-CCP antibody could be regarded as a new diagnostic marker for RA.