Literature data suggest that identification of the conditions preventing lecithin:cholesterol acyltransferase (LCAT) to produce normal cholesterol esterification might be of utmost importance in the follow-up of atherosclerosis (1-7). Interrelationship between LCAT activity, and total cholesterol (TC), unesterified cholesterol (UC), esterified cholesterol (EC), low and high density lipoprotein cholesterol (LDL-C, HDL-C), triglycerides (TG), phospholipids (PL), free fatty acids (FFA), 1-lactate (LAC), and electrolytes, i.e. zinc (Zn), calcium (Ca) and magnesium (Mg), was investigated in 60 patients with acute myocardial infarction (AMI), 30 patients with coronary heart disease (CHD) and 30 healthy control subjects. Results of the study revealed LCAT activity to be significantly decreased in atherosclerotic patients, with a significantly increased ratio of unesterified-esterified cholesterol (UC/EC), as compared to the control group of normal subjects. A decreased LCAT activity was accompanied by elevated values of phospholipids and LDL-C, a moderate increase in triglycerides, and a decreased quotient of HDL3/HDL2 cholesterol. Accordingly, a decreased activity of LCAT could with great certainty be considered a high-risk biochemical factor for atherosclerosis.