The findings of ultrasonography (US) of 52 tendons of the hands of 14 patients with chronic rheumatoid arthritis (RA) were compared with operative findings obtained subsequently. US showed tenosynovitis as expansion of a hypoechoic area around the tendon. US also enabled pattern classification based on shape, internal echo and border features of the scanned tendon, differentiation of acute and progressive stages among acute inflammation, invasion of tenosynovitis, degeneration, and rupture of the tendon to be made, and the progression of tendon lesions could be ascertained. It was found that in inflammation the tendon was significantly thickened, and in degeneration, the tendon was thinned. By dynamic US scanning, disturbances of tendon movement due to tendon rupture and adhesion to surrounding structures could be detected and differentiated. It was found in this study that preoperative US of the hand of RA patients is very useful for early diagnosis and for the selection of treatment including operative methods.