A procedure is described for the determination of triglyceride contained in low density lipoprotein with the measures that triglyceride-containing lipoprotein is reacted with a non-ionic surface-active agent which is synthesized from a block copolymer of propylene oxide and ethylene oxide, and that a triglyceride determination method is carried out. The procedure is particularly suitable for the in-vitro diagnosis of vascular disorders, in particular in the detection of coronary heart disease.