ECG gated 201Tl scintigraphy was compared to non gated images for detecting 2-3 vessel disease 1-3 months after a first uncomplicated myocardial infarction. In all, 111 patients on anti anginal treatment underwent coronary arteriography and stress thallium imaging; 39 showed single vessel disease (SVD), and 72 multivessel disease (MVD). Sensitivity of black and white analog images was 82% for SVD and 8% for MVD. Sensitivity of computerized colored static images was 87% for SVD and 33% for MVD. For gated images, sensitivity was 100% and 92% in patients with SVD and MVD respectively. Specificity for detecting MVD was 95% for black and white images, 77% for computerized colored static images, and 69% for ECG gated images. Thus, ECG gated exercise 201TL scintigraphy is useful for predicting the extent of coronary artery disease 1-3 months after myocardial infarction in patients on anti anginal therapy.