Until recently, the diagnosis of aortic dissection rested on aortography. The purpose of this study was to evaluate the diagnostic value of echocardiography in that disease and its ability to inform on the extent of the dissection and on the presence of associated lesions. Twenty-six patients (mean age 64 +/- 10 years) admitted for suspected aortic dissection were explored by echocardiography and the results were compared with those of angiography and/or anatomical findings. Echocardiography provided the diagnosis in 14 of the 16 patients with aortic dissection and excluded it in the remaining 10 patients. The sensitivity and specificity of the method were 87.5 p. 100 and 100 p. 100 respectively. The type of dissection was correctly determined in 90 p. 100 of the patients whose aorta had been totally explored by echocardiography. Aortic regurgitation and pericardial effusion were detected in 81 p. 100 and 50 p. 100 respectively of patients with aortic dissection. These results confirm the diagnostic value of echocardiography in dissection of the aorta. The extent of the lesion can only be evaluated when the whole of the aorta is visualized. The echocardiographic diagnosis is easier when the ascending aorta is involved (type I), while in type III aortic dissection there is a risk of missing a retrograde lesion of the aorta and confusing this type with type I. In this study two kinds of intimal flap motion were observed: in the first one the motion was independent of that of the aorta, while the second one resembled a division of the aortic, wall the motion of which is parallel to that of the aorta.