The incremental advantage of transesophageal echocardiography was determined by comparing results of paired transthoracic and transesophageal echocardiographic examinations performed in 61 patients for evaluation of suspected infective endocarditis. According to clinical and pathologic data, 31 of 61 (51%) patients had finding that were positive for infective endocarditis. Studies were graded as positive or negative for vegetations and were also graded for image quality. The sensitivity of transesophageal echocardiography in detecting vegetations was 88% versus 30% for transthoracic studies (p less than 0.01). For patients with aortic valve infective endocarditis, transesophageal sensitivity was 88% versus 25% for transthoracic sensitivity, because transesophageal echocardiography successfully separated vegetations from chronic valve disease caused by sclerosis or calcification (p less than 0.01). For patients with mitral valve infective endocarditis, transesophageal sensitivity was 100% versus 50% for transthoracic sensitivity, because transesophageal echocardiography distinguished vegetations from myxomatous changes or detected vegetations on prosthetic valves (p less than 0.01). Thus transesophageal echocardiography improves recognition of infective endocarditis, particularly in the presence of underlying valvular disease.