Although cardiac anomalies are well documented among children with Down's syndrome, data on the cardiac status of adults with Down's syndrome are sparse. Therefore, we performed cardiac auscultation and Doppler echocardiographic examinations in 35 asymptomatic adults with Down's syndrome. There were 25 men and ten women; their mean age ( ± SD) was 26 ± 8 years. Only ten subjects (29%) had normal findings on examination. The most frequent abnormal findings were holosystolic mitral valve prolapse (MVP) in 20 subjects (57%) and mild aortic regurgitation in four subjects (11%). Of the 20 subjects with MVP, five had associated tricuspid valve prolapse, but none had notable mitral regurgitation. Thus, we found that the majority of asymptomatic adults with Down's syndrome had valvular heart abnormalities. The high frequency of MVP and aortic regurgitation suggests that these lesions may be specifically associated with Down's syndrome in adults.