Ultrasound (US) is one of the most widely used tools for diagnosis and evaluation of carpal tunnel syndrome (CTS). US achievement is comparable to the gold standard electrophysiological studies. Depth of the carpal tunnel is a promising, relatively new sonographic parameter used for assessment of the median nerve. Previously it was evaluated in cadavers, normal individuals and in idiopathic carpal tunnel. The objective of this work is to address the value of the depth of the carpal tunnel (DCT) in patients with Carpal tunnel syndrome (CTS) and Rheumatoid arthritis (RA) by comparing it to healthy volunteers using US. Electrophysiology was used as a gold standard and other US parameters like cross sectional area (CSA) and flattening ratio (FR) were considered. The study was conducted in 123 non-diabetic RA patients having carpal tunnel syndrome (unilateral n=85, bilateral n=38) evidenced by electrophysiological diagnosis according to the criteria of the American Association of Electrodiagnostic Medicine. Furthermore, 40 hands from 20 healthy volunteers were examined. The mean age of the patients was 39.1±8.58 years. The female to male ratio was 96:27 in CTS patients. The difference between patients and healthy controls was significant in all three parameters and was highest at the DCT, followed by CSA and then FR. We can conclude that DCT increased obviously in RA patients with CTS, and this augmentation was related to tenosynovitis more than synovitis.