An arthrographic study of the wrist joint, in which 65 rheumatoid wrist joints were satisfactorily shown, gave a high incidence of significant abnormalities even in the absence of clinical signs of wrist involvement. Several synovial protrusion cysts were shown and corresponded to localized clinical swellings on the volar aspect of the wrist joint. These cystic swellings may be apparent before the onset of polyarthritis and may be differentiated from ganglia arthrographically by their association with other features suggesting erosive synovitis. Cystic swelling over the lower end of the ulna is shown to be frequently due to synovial hypertrophy of the inferior radioulnar joint in either a dorsal or volar direction. In one case a fistulous tract was delineated connecting the midcarpal joint with the volar surface of the wrist by a flexor tendon sheath.