Reinjection imaging with thallium-201 (201Tl) provides a reliable method of identifying viable myocardium. Reinjection of 201Tl immediately after completing the stress images followed by imaging 1 h after reinjection shortens the examination time to a maximum of 2.5 h and provides an alternative imaging approach in patients with coronary artery disease. In this study, we investigated whether immediate 201Tl reinjection imaging provides adequate information on myocardial viability compared with separate-day 201Tl rest or rest-redistribution imaging. In 23 patients with anterior or anteroseptal wall infarction first documented more than 3 months previously, we performed 201Tl stress-immediate reinjection, separate-day 201Tl rest imaging and rest-stress radionuclide angiography. In 13 patients, 201Tl rest scintigraphy was followed by redistribution imaging 3 h later. On the three-view planar 201Tl images, eight myocardial segments were analysed visually and quantitatively. Stress 201Tl images were compared with 201Tl reinjection images, 201Tl rest images and 201Tl 3-h redistribution images after rest injection. When comparing the stress images both with the immediate reinjection images and the rest images, concordant scintigraphic classification was found in 181 of 184 myocardial segments (kappa = 0.97). Comparing the stress images both with the immediate reinjection images and with the 3-h redistribution images following 201Tl injection at rest, concordant scintigraphic classification was found in 102 of 104 myocardial segments (kappa = 0.97). In 16 of 23 (70%) patients, 201Tl stress-immediate reinjection scintigraphy and radionuclide angiography provided concordant information on myocardial viability. In 6 (26%) patients, we observed a function-perfusion mismatch (i.e. 201Tl uptake in dyskinetic/adyskinetic regions) indicative of jeopardized but viable myocardium, demonstrating the additional value of 201Tl as a marker of viability. We conclude that stress-immediate 201Tl reinjection images provide information on myocardial viability and ischaemia in patients with previous myocardial infarction in addition to that obtained regarding wall motion abnormalities as assessed by rest-stress radionuclide angiography.