Transesophageal echocardiography (TEE) is commonly performed to detect the presence of a left atrial appendage (LAA) thrombus in the setting of an embolic event or before an anticipated electrical cardioversion for atrial fibrillation. The predictive value of transthoracic echocardiographic (TTE) findings in these patients has not been well defined. This study evaluated whether TTE findings can predict LAA thrombi using TEE as the gold standard for the identification of LAA thrombi. From November 1995 to March 2003, 10,753 patients underwent TEE to exclude LAA thrombi after embolic events or before cardioversion. Of these, 3,768 patients had complete TTE examinations performed <2 weeks before undergoing TEE. Demographics, TTE, and cardiac rhythm variables were analyzed using univariate and multivariate logistic regression to identify predictors of LAA thrombi diagnosed on subsequent TEE. LAA thrombi were identified by TEE in 199 patients (5.3%). Several TTE variables predicted LAA thrombi by TEE, including mitral stenosis, atrial fibrillation, tricuspid regurgitation, valvular prosthesis, left ventricular dysfunction, and right ventricular dysfunction. Mitral regurgitation was associated with a reduced risk for LAA thrombi (odds ratio 0.61, p = 0.003). A structurally normal heart in sinus rhythm (n = 247, 6.9%) had a 100% negative predictive value for LAA thrombi. In conclusion, several TTE variables were found to be predictive of LAA thrombi. The likelihood of LAA thrombi being found on TEE was infinitely small in the absence of these variables and the presence of sinus rhythm.