Carditis is the only manifestation of acute rheumatic fever that leads to permanent disability. Hence, its diagnosis is of paramount importance. Recently, it has been reported that Doppler echocardiography has disclosed subclinical valvar regurgitation in some patients with acute rheumatic fever manifested as isolated arthritis or pure chorea. The prognosis of such patients with acute rheumatic fever and subclinical valvitis is not clear. We aimed, therefore, prospectively to investigate the potential to diagnose patients with subclinical carditis. We examined 40 patients, aged from 7 to 16 years, with Doppler evidence of mitral and aortic regurgitation, but in the absence of any pathologic murmur. The major findings satisfying the Jones criterions were arthritis in 29 patients, chorea in 10 patients, and arthritis and erythema marginatum in one patient. Of the patients, 33 had mitral regurgitation, 6 patients had combined mitral and aortic regurgitation, and one patient had aortic regurgitation. The patients were followed over a mean period of 18.1 +/- 13.9 months, the valvar regurgitation disappearing in 23 (57.5%). No significant differences were observed in the resolution of the valvitis between those treated with acetylsalicylic acid, steroids, or those receiving no treatment. It is noteworthy, nonetheless, that patients treated with steroids were the fastest to recover from valvitis (p < 0.05). Based on our study, we suggest that subclinical valvitis demonstrated by echocardiography should now be accepted as adequate evidence for the diagnosis of carditis, and become a major diagnostic criterion for acute rheumatic fever. When managing this group of patients with subclinical disease, treatment with steroids seems to have a role in promoting early resolution of the valvitis.