Thallium-201 is very suitable for cardiac imaging because of its physical characteristics and biological behaviour. Perfusion defects caused by ischaemia, necrosis or fibrosis are represented by 'cold spots' on the myocardial scan. In this article we report our experience with this method in the diagnosis of ischaemic heart disease in 117 patients. Excellent correlation was found with clinical, electrocardiographic and angiographic parameters. Both sensitivity and specificity for the diagnosis of ischaemic heart disease were higher with /sup 201/Tl scintigraphy than with existing diagnostic methods.