The clinical manifestations of acute rheumatic fever were evaluated in a study of 35 adult patients. Migratory polyarthritis occurred in all but one. None had chorea, erythema marginatum, or subcutaneous nodules. Carditis occurred in eight, manifested by pericarditis in four and by development of new significant murmurs in four. Two patients died during their acute attacks, and nine exhibited new valve damage on follow-up. The results of the study indicate that rheumatic fever represents a continuous spectrum from childhood to adulthood, in which the incidence of carditis, though diminishing, remains significant. In addition, cardiac involvement may occur de novo in the adult, resulting in permanent damage or even death. This would have important implications regarding penicillin prophylaxis.