To clarify whether echocardiographic detection of a vegetation 10 mm or larger in size in patients with left-sided infective endocarditis poses an increased risk for complications, we performed a meta-analysis of English-language publications identified by a computerized search of the key words infective endocarditis and echocardiography. A pooled odds ratio was calculated by using the Robins, Greenland, and Breslow estimate of variance. The pooled odds ratio for increased risk of systemic embolization in the presence of a vegetation >10 mm (10 studies, 738 patients) was 2.80 (95% confidence interval [CI] 1.95 to 4.02; p < 0.01). The odds ratio of requiring valve-replacement surgery (seven studies, 549 patients) was 2.95 (95% CI 1.90 to 4.58; p < 0.01). The odds ratio of death (six studies, 476 patients) was 1.55 (95% CI 0.92 to 2.60; p = 0.10). Thus this analysis supports the hypothesis that echocardiographically detected left-sided vegetations >10 mm pose a significantly increased risk of (1) systemic embolization and (2) a need for valve-replacement surgery than cases where either no or smaller vegetations are detected.