In 168 patients with ischaemic heart disease an ergometric loading test on a bicycle ergometer was made before coronarography. A total of 19 patients had on coronarography a finding of significant stenosis of the lumen of the trunk of the left coronary artery--group A. These patients were compared with a control group of 20 patients with confirmed coronary heart disease (narrowing of the diameter of the lumen by 50 or more percent) without affection of the trunk of the left coronary artery-group B. As to the investigated parameters of the ergometric test the two groups differed significantly in the total time of the load (group A: 6.21 minutes, group B: 7.94 minutes, p < 0.05), while in all other parameters--total amount of performed work, sum of depressions of the ST segments during a maximum load, time of onset of stenocardias, time since development of 1 mm depressions of the ST segment, maximal depression of the ST segment in lead V5 and number of leads with ST depressions above 1 mm--no significant difference was found. From the work ensues that from the ergometric loading test the finding of stenosis of the left coronary artery on coronarography cannot be predicted.