To assess clinical significance of transient ischemic dilatation of the left ventricle (TID) on dipyridamole-stressed 201Tl myocardial scintigraphy, 110 patients suspected with coronary artery disease, including 13 with normal coronary, 48 with single vessel disease, 30 with 2 vessel disease, and 19 with 3 vessel disease were analyzed. TID was visually and quantitatively assessed calculating the ratio of the area within the left ventricular region on the initial and delayed image (TID ratio). TID was observed in 3 of 1 vessel disease (6%), 5 of 2 vessel disease (17%), and 8 of 3 vessel disease (42%). None of normal coronary artery showed TID. In patients with multivessel disease (MVD), TID was observed more frequently (27%) than in patients with 1 vessel disease (6%) (p < 0.025). Furthermore, the TID ratio tended to be higher (1.15 +/- 0.11) than those with single vessel disease (1.03 +/- 0.03). To identify patients with MVD, TID had a sensitivity of 27% and a specificity of 95%. ECG changes were observed more often in patients with TID than those without TID. Five patients showing TID underwent coronary artery bypass graft surgery, TID disappeared postoperatively in each patient. In conclusion, TID on dipyridamole 201Tl scan seems to be a specific although not sensitive marker for detecting MVD.