Stress T1-201 myocardial scintigraphy was carried out in 16 patients with x-syndrome. Eleven patients having IHD with single-vessel disease served as the control. With bicycle exercise test all 16 patients with x-syndrome had some type of myocardial perfusion abnormality. These perfusion defects were situated in the vascular beds of different coronary arteries. Myocardial perfusion defects in patients with x-syndrome were similar to those patients with moderate, but haemodynamically significant, single-vessel disease. At the same time, these perfusion defects were significantly less pronounced than those in patients with a subtotal occlusion of one coronary artery. Thus, patients with x-syndrome have not only the clinical features of IHD (anginal attacks), but also marked stress-induced, myocardial perfusion defects.