Sonography of the hands is especially helpful in the diagnosis of early arthritis. Sonography allows for a very sensitive detection of small joint-effusion, tenosynovitis and small erosive bone lesions earlier than conventional radiography. Musculoskeletal sonography is also helpful in morphological analysis of changes of the median nerve in patients with carpal tunnel syndrome. The following standard scans are suggested for the sonographic evaluation of the wrist: 1. dorsal longitudinal scan along the radio-carpal joint, 2) along the ulno-carpal joint, and 3) dorsal transverse scan along the wrist to detect joint fluid collection, synovitis, tenosynovitis, ganglia, irregularities of the bone surface in osteoarthritis, and erosions due to inflammatory disease, 4) volar longitudinal scan along the radio-carpal joint, and 5) along the ulno-carpal joint, and 6) volar transverse scan along the wrist to diagnose the same objective as the above mentioned scans and to evaluate the median nerve in cases of carpal tunnel syndrome. Optional scans are the following: 7) ulnar longitudinal 8) transverse scan along the ulnar joint space and the extensor carpi ulnaris muscle to detect tenosynovitis and caput ulnae syndrome, 9) radial longitudinal, and 10). transverse scan along the joint space to diagnose synovitis and tenosynovitis. The following standard scans are suggested for the sonographic evaluation of the fingers: 1) volar longitudinal, 2) volar transverse scan in extension along the finger joints to detect effusion and synovial proliferation, tenosynovitis, irregularities of the bone surface (osteophytes, erosions), 3) dorsal longitudinal scans in extension and flexion >70 degrees along the CMC I, MCP, PIP and DIP joints to evaluate effusion and synovial proliferation, tenosynovitis or tendinitis, irregularities of the bone surface (osteophytes, erosions), and 4) dorsal transverse scans along the finger joints to evaluate these structures in an additional dimension. Optional 5) scans include the following: medial longitudinal scan along the MCP I, II, PIP and DIP joints, and 6) lateral longitudinal scan along the MCP V, PIP and DIP joints to evaluate the erosive bone process and joint instability. A linear transducer with a frequency of between 7.5 and 12 MHz is recommendable. The anterior distance between the bone and the joint-capsule of the wrist is > or = 3 mm in probable and > or = 4 mm in definite synovitis or effusions. Synovitis or effusions are probable if the difference between right and left wrist is > or = 1 mm, and they are definite if the difference is > or = 2 mm. A carpal tunnel syndrome is probable with a cross-sectional area of the median nerve of > or = 12 mm(2).