In 60 patients myocardial infarction size was determined by electrocardiogram (ECG) using Selvester's QRS scoring system. These values were compared with the size of infarction as determined enzymatically using gram equivalent isoenzyme MB creatine kinase (gEq) and using maximum values of isoenzyme MB-CK. The results showed no statistically significant difference between the size of anterior and inferior infarction determined by gEq (25.19 +/- 13.59 vrs 22.48 +/- 14.04; p = 0.12 NS) and by maximum MB-CK (125.5 +/- 76.0 vrs 98.4 +/- 60.7; p = 0.12 NS). The size of myocardial infarctions determined by ECG was significantly larger anteriorly compared with the inferior infarcts (9.6 +/- 2.9 vrs 4.5 +/- 2.6; p = 0.001). In patients with anterior infarcts good correlations between the size of infarction determined by QRS scoring system and by gEq or maximum MB-CK were found (r = 0.69; p = 0.004 and r = 0.72; p = 0.001). In patients with inferior infarcts the correlations between QRS score and gEq or maximum MB-CK were poor (r = 0.37; p = 0.02 and r = 0.45; p = 0.15). The causes of weak correlations in the results of described methods in inferior infarcts are discussed. Thus QRS scoring system provides new noninvasive and simple possibilities in determining the size of anterior and in inferior infarctions of the left ventricle.