One hundred consecutive patients undergoing left ventricular aneurysmectomy were reviewed to determine the incidence of associated mural thrombus, the accuracy of angiography in detecting thrombus, and any effect of anticoagulant therapy on the incidence of thrombus and embolism. Thrombus was present in 48% of cases and was located in antero-apical aneurysms in all but two cases. Angiography resulted in correct diagnosis of thrombus with a sensitivity of only 31% and a predictive accuracy of 54%. Presence of mural thrombus correlated inversely with duration of anticoagulant therapy. Embolism occurred in 5% of patients with left ventricular aneurysm.