It has been suggested that tarsal arthritis with ankylosis may be characteristic of late onset Still's disease. In our study 16 of 88 (18%) patients with juvenile rheumatoid arthritis (JRA) and 22 of 97 (23%) patients with adult RA had radiographic findings of tarsal joint ankylosis. In our patients, tarsal bony fusion was not related to type of disease onset, age of onset or sex; rather it was related to a longer duration of disease. Tarsal ankylosis should not be regarded as a special feature of Still's disease since it can also be seen in adult RA.