We undertook this study to determine the use of transthoracic and transesophageal echocardiography in detecting valvular perforation and the clinical impact of the latter on the outcome of left-sided infective endocarditis. Transthoracic echocardiography was performed in 58 consecutive patients with infective endocarditis. According to the study protocol, a subgroup of 42 patients also underwent transesophageal echocardiography. At referral, 20 (34%) of 58 patients had echocardiographic evidence of valvular perforation (group A). No valvular perforations were found in the remaining 38 patients (group B). During a follow-up period of 27 ± 16 months, a major complication occurred in 18 of 20 patients in group A and in 11 of 38 patients in group B (p < 0.0001). Univariate analysis indicated previous infective endocarditis, aortic involvement, and New York Heart Association functional class had a predictive value for valvular perforation (p < 0.001). Stepwise regression analysis confirmed aortic valve perforation as the only independent predictive variable for surgery and death. Valvular perforation is a common complication of infective endocarditis and is associated with an adverse outcome. Transthoracic echocardiography can detect or suggest valvular perforation in infective endocarditis, but transesophageal echocardiography better defines this complication and predicts severe heart failure or the need for early surgical management. (Am Heart J 1997;134:656-64.)