Sonography of joints and peri-articular soft tissue has become an established imaging technique for the diagnosis and follow-up of patients with rheumatic diseases. Sonography allows a good differentiation of exsudative and proliferative changes of synovialis as well as tenosynovitis. Superficial cartilage and bony lesions may be seen before they are apparent on x-rays. Sonography is helpful in the diagnosis of early arthritis. Dynamical examination of joints allows the detection of structural abnormalities. Sonography can also be used for interventional procedures such as joint aspirations, guidance of therapy and needle biopsy.