Abstract Aim of the work: Assessment of synovitis in rheumatoid arthritis (RA) is a major issue for proper treatment; it has been proven that high resolution musculoskeletal ultrasound (MSUS) examination could be of valuable help. The B-cell chemokine , CXCL13, is a novel serum biomarker of synovitis in RA. We aimed to find out the presence of synovitis in patients with RA and its correlation with disease activity. Patients and methods: We evaluated 30 patients with RA for the presence and degree of synovitis by performing high resolution MSUS and obtaining serum CXCL13 levels. In addition, we correlated these results with disease activity score 28 (DAS 28). Results of serum CXCL13 levels were also obtained for 20 healthy age- and sex-matched subjects served as controls. Results Serum CXCL13 level was significantly increased in RA patients vs. controls (p < 0.001). High resolution MSUS revealed that RA patients had a significant increased synovial thickness. In RA patients, DAS 28 had a significant correlation with serum CXCL13 ( p