We evaluated the clinical application of echocardiography (M and 2D modes) in the assessment of cardiac patients with fever and an underlying valvular abnormality in whom the diagnosis of infective endocarditis was suspected. One or more of the classic clinical features of the disease were present in 50 patients (group A). Vegetations were detected by echocardiography in 17 (47%) out of the 36 patients within this group A who had positive blood cultures. Four (28.5%) of the remaining 14 patients with unequivocal endocarditis clinically and negative blood cultures had demonstrable vegetations on ultrasound. Anatomical complications resulting from the septic process (valve destruction or detachment, aortic root abscess) were visualized in 18 (36%) of the 50 patients in group A. The clinical features of endocarditis were lacking in the other 53 patients with fever and murmur (group B). This group included 12 patients with other sources of bacteraemia besides endocarditis. Unsuspected vegetations were detected only in 2 (3.7%) out of the 53 cases. Thus echocardiography is useful in confirming the clinical diagnosis of infective endocarditis, but only rarely detects vegetations in patients who lack the characteristic clinical features of endocarditis, regardless of whether they have positive negative blood cultures.