Immediate reinjection of thallium-201 after acquisition of the stress images followed by imaging 60 min later has been proposed as a novel time-saving and patient-convenient approach for the evaluation of myocardial ischaemia and viability. The objective of this study was to establish the clinical value of thallium-201 stress immediate reinjection imaging in the evaluation of patients with suspected and known coronary artery disease. Quantitative planar thallium-201 stress immediate reinjection imaging was performed in 138 patients with undiagnosed chest pain, of whom 114 underwent cardiac catheterization and 24 had a < 5% likelihood for coronary artery disease; 56 patients had previously suffered a myocardial infarction. Sensitivities and accuracies were determined for coronary artery disease, reversible myocardial ischaemia, and myocardial viability. Of the 138 patients studied for coronary artery disease, thallium stress scintigraphy identified 85 of 93 patients with angiographically proven coronary artery lesions (overall sensitivity 91%). The normalcy rate in the low-likelihood patients was 88% (21 of 24 patients) and the overall diagnostic accuracy was 83%. In the 56 patients who had suffered a previous myocardial infarction, and in whom the suitability for reversible ischaemia was sought, the overall patient-related sensitivity and accuracy were 93% and 92% respectively. In the 56 patients with a previous myocardial infarction a total of 168 vessel regions were studied to detect viability. Of the 142 normal or hypokinetic regions, 127 regions were scintigraphically identified as viable (sensitivity 89%). The thallium stress immediate reinjection imaging protocol is an appropriate clinical approach in patients with undiagnosed chest pain. The combined identification of stress-induced ischaemia and viability by thallium stress immediate reinjection imaging provides adequate algorithms allowing optimal management and risk assessment in the individual cardiac patient.