Abstract
In 73 patients suffering from Reiter''s disease, radiologic evidence of disease of the sacro-iliac joints was found in half. Backache and stiffness were frequently present but root pain was observed only when there was extension to the lumbo-sacral plexus. Sacro-iliac disease is probably much more common in Reiter''s disease than has been thought, and is frequently associated with recurring attacks of iritis.