Abstract: Rheumatoid arthritis (RA) is a chronic, multisystem autoimmune disease which manifests itself in multiple joints of the body. It is characterized by infiltration of inflammatory cells such as monocytes and it is believed to be the result of a faulty immune response.       Chemokines play a major role in selectively recruiting monocytes, neutrophils, and lymphocytes, as well as in inducing chemotaxis through the activation of G-protein-coupled receptors. Monocyte chemoattractant protein-1 (MCP-1/CCL2) is one of the key chemokines that regulates migration and infiltration of monocytes/macrophages. Aim of The Work: was to study the role of serum Monocyte chemotactic protein-1 (MCP-1) in patients with rheumatoid arthritis as a diagnostic and prognostic marker and the possible association with disease activity. Subjects and methods: Forty   rheumatoid arthritis diseased patients were selected  , they were 3 males and 37 females. The patients were categorized into two groups according to activity of the disease regarding DAS score . Another 20 healthy subjects, 2 males and 18 females, with no history of rheumatoid disease were recruited as controls .Results: this study showeda highly significant increase in MCP-1 and ESR in all rheumatoid arthritis patients groups   , active rheumatoid arthritis patients group and inactive rheumatoid arthritis patients group compared to control group.      Correlation study of serum MCP-1 revealed a significant positive correlation between serum MCP-1 and ESR and DAS score in all patients versus the healthy group and a significant positive correlation between serum MCP-1 and ESR in the active group. ROC curve analysis was showing the diagnostic performance of serum MCP-1 in   rheumatoid   arthritis patients(active and inactive) versus the healthy control group, at a cut-off level of 52.5 ng/ml., the diagnostic sensitivity, specificity, negative predictive value and positive predictive value were 98%, 93%, 93% and 98% respectively   Also, it shows the diagnostic performance of serum MCP-1 in discriminating active  rheumatoid   arthritis patients from the inactive group, at a cut-off level of 61ng/ml Conclusion: - Serum MCP-1 is one of the best indicator of clinical arthritic activity in RA patients. It  represents a novel, independent indicator of clinical arthritic activity that also provides a good reflection of effect of treatment in rheumatoid arthritis patients.