Sixty-two patients with the clinical evidence of infective endocarditis (IE) were studied by two-dimensional echocardiography (2DE). All patients underwent surgical operation or autopsy after 2DE examination and 2DE diagnosis was compared with pathological findings. In all 62 patients, 47 vegetations (76%), 31 valvular perforations (50%) and 18 ruptured chordae tendineae (29%) were detected at surgery or autopsy. Vegetations were detected in 40 out of 62 (65%) patients by 2DE. Sensitivity of 2DE diagnosis of vegetation was 85% (40/47), specificity was 20% (3/15), predictive value of positive test was 77% (40/52) and that of negative test was 30% (3/10). In 32 cases with aortic valvular lesion, seven cases were falsely diagnosed as vegetative lesions by 2DE (22%). The characteristics of vegetations by 2DE in false positive cases were nodular shape and less than 10 mm in the longest diameter. These lesions were proved to be perforation or fibrous thickening of the valve at surgery or autopsy. In 25 cases with mitral valvular lesion, 5 (20%) were falsely diagnosed as vegetations by 2DE. They also have nodular shape and smaller than 10 mm in the longest diameter by 2DE. Pathological findings of these cases were proved ruptured chordae tendineae, granulous tissue and valvular thickening. There were seven false negative cases (aortic 2, mitral 3, tricuspid 2). 2DE diagnoses of these cases were valvular thickening and ruptured chordae tendineae, but only small vegetations were found during surgery. This study revealed limited reliability of 2DE diagnosis on vegetation, especially low specificity and predictive value for negative test. Difficulties in detection of valvular perforations (23%; 7/31) and ruptured chordae tendineae (33%; 6/18) by 2DE were major causes of false positive diagnosis. In the clinical setting where IE is strongly suspected, 2DE findings must be interpreted with caution.