M-mode and two-dimensional echocardiographic evaluation of infectious endocarditis and its complications was reviewed. In 21 consecutive patients with clinical endocarditis, 22 valves were involved (12 aortic, 5 mitral and 5 tricuspid). M-mode echocardiography detected vegetations in 10 patients (four aortic, two mitral and four tricuspid) and detected complications of endocarditis in 2 patients (one aortic root abscess and one flail aortic cusp). Two-dimensional echocardiography detected vegetations in 9 patients (four aortic, one mitral and four tricuspid) and detected complications in ten patients (five flail aortic cusps, one aortic root abscess, one sinus on Valsalva aneurysm, two flail mitral leaflets and one flail tricuspid valve). Thus, although M-mode and two-dimensional echocardiography had a similar ability to detect actual vegetations, two-dimensional echocardiography was superior to M-mode echocardiography in diagnosing complications of the destructive process.