OBJECTIVE Echocardiography has become a widely utilized test since its introduction into clinical medicine in the early 1970s. Although it has frequently been performed in patients suspected of having mitral valve prolapse (MVP), its usefulness in this setting has not been systematically studied. To investigate the use and value of echocardiography in patients suspected of having MVP, we conducted a prospective study in which physicians were interviewed before and after ordering echocardiographic testing for patients in whom there was a suspicion of MVP. METHODS The study population included consecutive patients referred to the echocardiography laboratory at Boston University Medical Center because of suspected MVP between January 1 and December 31, 1987. Two standardized telephone interviews were conducted with the physician most responsible for ordering the echocardiogram. The following information was obtained during the first interview, which was always conducted before the echocardiogram was performed: patient demographic and clinical data; the reason for ordering the echocardiogram; the physician's most likely clinical diagnosis; the physician's estimate of the likelihood that the patient had MVP; and the physician's proposed management plans. After the referring physician received the echocardiographic results, a second interview was conducted to determine changes in the most likely clinical diagnosis and management plans. The impact of the echocardiogram on diagnosis and management was evaluated by comparing physician responses before and after reception of echocardiographic results. Receiver operating characteristic (ROC) curves were constructed to assess the physician's skills at distinguishing patients with echocardiographic-documented MVP from those without MVP. RESULTS A total of 106 echocardiograms were ordered by 45 different physicians. More than 80% of all echocardiograms were ordered to address diagnostic or therapeutic concerns. On echocardiography, 47 (44%) patients were found to have MVP, six (6%) had mitral regurgitation without prolapse, and 53 (50%) had normal results. On the basis of the ROC curve analysis, the physician's ability to discriminate between patients with and without echocardiographic MVP varied significantly by physician specialty and practice setting. The echocardiographic results led to a change in diagnosis in 59 (56%) patients. A change in management occurred in 29 (27%) patients, with 25 of these 29 changes (86%) related to the initiation or discontinuation of antibiotics. CONCLUSIONS Echocardiography frequently alters diagnostic assessments and leads to therapeutic changes in some patients suspected of having MVP. However, the benefits of such changes have not yet been demonstrated.