THE CONCEPT that rheumatic fever may cause a deforming arthritis which superficially simulates rheumatoid arthritis apparently is accepted on the Continent and in England, while its validity has yet to be demonstrated to the satisfaction of most American rheumatologists.1,2 The possibility still remains that chronic postrheumatic-fever (Jaccoud's) arthritis is merely an unusual variant of rheumatoid arthritis coincidentally occurring in a patient with rheumatic valvular heart disease.3,4 In an attempt to more clearly define and differentiate this deformity from rheumatoid arthritis, definite criteria for it have been proposed by Bywaters 5 and Zvaifler.3 More recently summarized by others,4 these criteria consist of repetitive attacks of rheumatic fever distinguished from rheumatoid arthritis by the presence of migratory polyarthritis and rheumatic valvular heart disease; recovery from the attacks with minimal residual stiffness of the metacarpophalangeal joints; the insidious and painless appearance some months to years later of a voluntarily