A retrospective study on the clinical features of acute rheumatic fever (RF) with carditis in 45 patients, 15 years of age and older (range 15-61), is described. Nineteen patients were seen at initial attack; the remaining 26 patients (28 recurrences) were admitted because of RF recurrence. Of the total 47 episodes, carditis was manifested by a significant murmur without previous RF or any known rheumatic heart disease in 40%; change in the character of a murmur under observation or the appearance of a new murmur in 15%; and acute pericarditis in 19%. Congestive heart failure of recent onset was noted in 85% of the episodes, while classical polyarthritis or polyarthralgia occurred in 57%. The aortic valve was newly damaged or preexisting aortic regurgitation worsened in 12 episodes. Twenty-nine patients were followed for 1/2-16 years. Of 11 patients with an initial attack who were maintained on regular prophylaxis (intramuscular benzathine penicillin 1,200,000 units every 4 weeks), the mitral valve murmur disappeared in 3 and none of the patients had recurrence. Of the remaining 18 patients with no or incomplete prophylaxis, 1 died from congestive heart failure 6 months later, and 3 had recurrences with involvement of the aortic valve. In conclusion, RF with carditis in adolescents and adults in our practice at the National Taiwan University Hospital is likely to show more cardiac problems and complications than that seen in the West. Although active rheumatic carditis among this patient population is relatively uncommon, recurrences with subsequent involvement of the aortic valve (aortic regurgitation) do occur.(ABSTRACT TRUNCATED AT 250 WORDS)