OBJECTIVE: To study the frequency and features of joint and tendon involvement in the hand of patients with primary Sjögren's syndrome (pSS) by musculoskeletal ultrasound (US) examination. METHODS: Forty-eight patients with pSS diagnosed according to the preliminary classification criteria proposed by the American-European Classification Criteria Group were enrolled in the study. Bilateral US examination of the 1st-5th metacarpophalangeal (MCP), 2nd-5th proximal interphalangeal (PIP) joints and of flexor tendons were performed. A semi-quantitative grading method (0 to 3) for scoring joint effusion, synovial proliferation and intra-articular power Doppler (PD) signal was used. RESULTS: We observed clear evidence of inflammatory arthritis in 9 (18.7%) patients. Bone erosions at MCP and/or PIP joint were visualized in 6 out of 48 (12.5%) patients. In 10 (20.8%) patients we imaged flexor tenosynovitis which appeared more frequent than in healthy subjects even if no statistically significant difference was detected. CONCLUSION: US examination appears to be a useful imaging technique to study joint and soft tissue involvement in connective tissue diseases. The presence of bone erosions in pSS patients is unexpected. Future studies will hopefully concentrate more on defining the erosive capability of connective tissue disorders together with inflammatory involvement of tendons