Fifty-three of 83 patients with transmural perfusion defects had a “black hole” within the left ventricle on Tl-201 SPECT images. A “black hole” was defined as a focal, oval area of no activity within the left ventricular cavity adjacent to the transmural perfusion defect. 30 patients had only transmural perfusion defects with no “black hole”. Transmural defect is defined as an area of decreased perfusion with activity equal to or less than background. All had contrast ventriculography and/or echocardiography or gated blood pool studies. Fifty out of 53 patients with a “black hole”, and one out of 30 patients with only a transmural defect had left ventricular aneurysm. Of these 50 true positives, 13 had parallel, 10 had converging and 27 had a diverging configuration of the left ventricle walls towards the apex. In the three false positives two had parallel and one had converging left ventricle walls. The criterion of a “black hole” for the diagnosis of left ventricular aneurysm in patients with transmural myocardial perfusion defect had a 98% sensitivity, 91% specificity, 95% accuracy and 94% predictive value. Combining the criterion of diverging configuration of left ventricle walls with transmural perfusion defect and a “black hole” increased the predictive value for left ventricular aneurysm to 100%. Thus the “black hole” sign in Tl-201 SPECT images is highly accurate in the diagnosis of left ventricular aneurysm.