Ultrasonography of the hand and wrist was performed on 14 patients with definite rheumatoid arthritis. A hypoechoic thickening of the extensor tendon sheaths was noted, especially in the MP joint, which may be caused by rheumatoid tenosynovitis. The extensor tendon in the MP joint was also thickened. Cortical erosion of the articular bone in the MP joint could be easily distinguished. Some of the transverse scan of the volar aspect of the MP joint showed hypoechoic thickened sheath of the flexor tendon with highechoic flexor tendon. In some cases, the extensor tendons in the wrist were embedded in the hypoechoic tendon sheath with transverse scan of the dorsal aspect of the wrist. The ulnar head was surrounded by a hypoechoic cavity with longitudinal scan. In conclusion ultrasonography seems to be useful for diagnosis of tenosynovitis.