Fifty four workers (28 males and 26 females) from a chemical plant were studied. The basic lipid indices--cholesterine and triglycerides were determined. The population group examined was almost homogenous as regards age and lipid state. The level of HDL-cholesterine was determined after HDL separation via dextran sulphate and MgCl2 sedimentation. The analysis was performed after the extraction of the lipid component. In another part of the extract, cholesterine esters were determined via Ag+-thin layer chromatography, according to density rate of fatty acids in its composition. The patients were provisionally grouped according to the data on HDL-cholesterine, namely--under and over and 35 mg% (males) and 45 mg% (females). The level of cholesterine--linoleate and arachidonate were discussed in the thus differentiated groups of the examined. HDL was presumed to eliminate not only cholesterine from the peripheral tissues but to regulate the level of the system linoleic--arachidonic acids, being genetically associated with biosynthesis of prostaglandin-like substances. The high HDL level in serum, regulating the substrate provision for biosynthesis of prostaglandin-like substances is also admitted to contribute to the equilibrium in the physiological activity of prostaglandin-antagonists as well.