We evaluated sensitivity, specificity and predictive values of echocardiography in detecting aortic dissection. We studied in the same period of time two groups of consecutive patients with good quality echocardiographic examination. Group I, with high prevalence of the disease (76%), was composed of 25 patients; 19 patients with aortic dissection (11 of the type A and 8 of the type B) and 6 patients with clinical and echocardiographic suggestion of aortic dissection which was not confirmed by angiography. Group II, with lower prevalence of the disease (4%), was composed of 382 adult patients who underwent aortic angiography for different reasons. In this second group there were 16 out of the 19 patients of the first group, with aortic dissection, who underwent aortic angiography and the 6 patients with suspicion of aortic dissection which was not confirmed by angiography. Type A dissection: The finding of intimal flap on echocardiography was highly specific (98%) but relatively insensitive (45%); its positive predictive value was low (50% in the first and 34% in the second group). The specificity of increased thickness of aortic wall was lower (89%) and the sensitivity higher (81%); its positive predictive value was satisfactory in the first group (81%) and very low in the second (13%). Aortic root dilatation was fairly specific (76%); the sensitivity of this finding was high (87%) but its positive predictive value was still low (66% in the first and 7% in the second group). To conclude: the positive predictive value of the 3 echocardiographic signs of aortic dissection varied, in relation to the different prevalence of the disease, from 50, 81 and 66% in the first group to 34, 13 and 7% in the second group; the diagnostic utility of the echocardiographic examination appeared limited, in these patients, by the low values of sensitivity and positive predictive values; aortography is still the most valuable technique in the diagnosis of aortic dissection; echocardiography was useful in the early evaluation of some emergency cases (chest pain, shock, collapse...) suggesting sometimes the correct diagnostic hypothesis of aortic dissection; in the presence of a typical clinical picture, the contemporary presence of the 3 echocardiographic signs, though having the lowest sensitivity (36%), was highly predictive of the type A dissection. Type B dissection: In these patients the clinical picture, in contrast with type A dissection, Type A, was not indicating careful and complete echocardiographic aortic scan. Then the echocardiographic examination was even more disappointing: sensitivity 25%.