Although rheumatoid spondylitis is one of the most crippling of the chronic diseases affecting the spine, it has evoked but little interest except among rheumatologists and orthopedists. Contrary to general belief, the disease is a fairly common cause of chronic back complaints in young men. Often the diagnosis is not established for several years after the onset, and the early symptoms are frequently mislabeled as lumbago, fibrositis or muscular rheumatism, chronic low back strain, kidney disease or idiopathic sciatica. If physicians are alert, however, to the characteristic clinical and roentgenographic features of the disease, diagnosis should not be difficult even in the early stage. A surprisingly large number of soldiers with chronic back disability suffer from rheumatoid spondylitis; 18 per cent of patients with chronic back complaints admitted to an army general hospital were found to have this disease. The majority of these were early or relatively early cases. Such