Forty-seven echocardiograms were obtained in 32 patients with bacterial endocarditis. Preexistent abnormalities were found in 14 patients. In five of them thought to have bacterial endocarditis on normal valves, echocardiography showed mitral stenosis (one), bicuspid aortic valve (two), and prolapse of mitral valve (two). Definite vegetations were seen in 22 patients--on the aortic valve in seven, the mitral valve in 12, and both valves in three. Ten patients had milder changes suggestive but not diagnostic of vegetations. In 12 patients, surgery confirmed the echocardiographic findings. Fourteen had systemic embolic episodes and all had echocardiographic evidence of vegetations. Abnormalities secondary to bacterial endocarditis, other than vegetations, were common. Twenty-one patients had left ventricular volume overload. Ten had a flail posterior leaflet of the mitral valve, three of which were confirmed surgically. Eight had abnormal coarsely fluttering echoes in the left ventricular outflow tract consistent with a prolapsing aortic valve or underlying aortic vegetations; four were confirmed by surgery. Five had signs of severe aortic regurgitation of recent onset (premature mitral valve closure) and all had confirmation by surgery. Echocardiographic abnormalities persisted after successful medical treatment. We conclude that echocardiography is helpful in patients with bacterial endocarditis. It permits recognition of unsuspected preexistent lesions and the characteristic vegetations, as well as the extent and nature of valvular damage secondary to bacterial endocarditis. However, echocardiography does not differentiate between active and healed lesions.