The serum levels of lipids and lipoproteins were measured in 501 workers engaged in petrochemical industry and 100 control men. Highly elevated cholesterolemia, triglycerolemia with decreased serum phospholipid and lipoprotein concentrations are strictly characteristic in petrochemical industrial workers. There was a clear-cut relation of these changes to the nature of the type of production, age, especially to the length of service in petrochemical industry. The findings suggest that the nature of a chemical agent, the time of a lesion might play a significant role in the development of an atherosclerotic process in workers engaged in petrochemical industry.