M-mode and two-dimensional echocardiograms of 77 patients with infective endocarditis were examined to determine if presence and/or size of vegetations on echocardiogram were predictive of morbidity and mortality. Patients with (n = 43) or without (n = 34) vegetations on echocardiogram did not differ significantly in the proportions developing congestive heart failure (23 of 43 or 53% vs 12 of 34 or 35%) or emboli (11 of 43 or 24% vs 6 of 34 or 18%), whereas a slightly lower proportion of those with vegetations required surgery (5 of 43 or 12% vs 7 of 34 or 21%) or died (3 of 43 or 7% vs 4 of 34 or 12%). No significant relationship was found between vegetation size and the frequency of complications, the need for surgery, or death. In contrast, patients whose echocardiograms demonstrated premature mitral valve closure or chordal or cusp rupture had a significantly higher incidence of heart failure (10 of 13 or 77% vs 22 of 60 or 37%, p less than 0.003) and surgery (3 of 13 or 23% vs 7 of 60 or 12%, p less than 0.05). We conclude that: the presence of vegetation on the initial echocardiogram is not predictive of the clinical course in infective endocarditis; vegetation size does not predict complications, need for surgery, or death; but valve cusp or chordal rupture and/or premature mitral valve closure are associated with congestive heart failure and the need for surgery.