Cardiac sources of emboli have been frequently described in patients with Transitory Ischemic Attacks (TIAs). The aim of our study was to assess the value of two-dimensional echocardiography (2D-E) in the investigation for possible cardiac aetiology of TIAs. As an offshoot of a larger epidemiologic study which aimed at determining the period prevalence of TIAs in 6.504 subject(s) of the general population aged between 40-65, fifty subjects with TIA (group A) and 66 controls (group B) were studied. A heart disease was found in 20/50 s. (40%) in group A (coronary artery disease: 5; hypertensive heart disease: 4; mitral valve prolapse: 5; left ventricular aneurysms: 2; aortic valve disease: 2; aortic valve prosthesis: 1; atrial fibrillation: 1) and in 5/66 s. (7.5%) in group B (p less than 0.01) (coronary disease: 2; hypertensive heart disease: 1; mitral valve prolapse: 2). A potential source of emboli was present in 11 s. in group A (22%) and in 2 s. in group B (3%) (p less than 0.01). In 4/50 s. in group A and in 1/66 in group B the diagnosis was obtained by means of 2D-E only, because other clinical signs and ECG data were negative. 2D-E could only confirm the diagnosis in the remaining cases, with no additional information (i.e., no intracavitary masses were seen). In conclusion there is a high prevalence of heart disease in patients with TIA over 40 years of age. A cardiac source of emboli may be suspected in a substantial number of cases. Nevertheless the value of routine 2D-E in disclosing an otherwise undetected source of emboli is rather low.