The value of 2-dimensional echocardiography (2-D echo) in patients with suspected ascending aortic dissection was assessed. During a 5.5-year period, 56 consecutive patients underwent bedside 2-D echo for unexplained chest pain possibly due to ascending aortic dissection. Patients with obvious aortic dissection who proceeded directly to aortography were excluded and in all 56 study cases, 2-D echo was the initial diagnostic test. Using standard criteria, 2-D echo correctly identified all 13 patients with ascending aortic dissection. There were 5 false-positive study results and 38 true-negative results, yielding a sensitivity of 100%, specificity of 88% and overall diagnostic accuracy of 91%. In the group of 13 patients with confirmed ascending aortic dissection, 2-D echo identified 4 with pericardial fluid, and 3 of these patients (75%) died within 24 hours. In comparison, 7 patients in the group of 43 without confirmed dissection had pericardial fluid by 2-D echo and only 1 died (p less than 0.001). Finally, in the group of 38 patients with true-negative results, 2-D echo provided useful information in 16 (42%) that assisted or was essential in establishing an alternative diagnosis. However, 5 patients in this group had type III dissection and in none was it identified by 2-D echo. Thus, our data indicate that 2-D echo represents a reliable noninvasive method for rapidly diagnosing ascending aortic dissection at the bedside; offers important prognostic information which is directly related to the presence of pericardial fluid, and provides useful additional information which assists or establishes an alternative diagnosis when ascending aortic dissection is absent.(ABSTRACT TRUNCATED AT 250 WORDS)