Changes in ST-T complex were studied using Holter electrocardiographic monitoring in 83 male patients with stable angina of effort. Episodes of transitory ST displacement were detected in 74.8% of patients. Of the recorded 886 ST displacement episodes, ST depression was seen in 35.9% of cases, with accompanying anginal pain in 88.4% of those. ST elevation was seen in 64.1% of cases, but anginal pain only accompanied a more than 2 mm elevation in 3.2% of those, while 96.8% of 1-2 mm elevations were asymptomatic. Total duration of ST depression was found to be an objective criterion for the assessment of the severity of stable angina of effort, amounting to less than 1% of the day in patients referred to functional class (FC) 1, 1-4% in FC 2, 5-10% in FC 3 and more than 10% in FC 4.