Triglyceride is found in all plasma lipoproteins but is the major lipid component of those lipoproteins with a density< 1.019 kgfL. These triglyceride-rich lipoproteins encompass a spectrum of lipoproteins in terms of size, density, and lipid and apolipoprotein composition and include chylomicrons, chylomicron remnants, verylow-density lipoprotein(VLDL), and intermediate-density lipoprotein(IDL). Because the catabolic processes involved in VLDL and IDL metabolism are similar to those for chylomicrons, defects in their catabolism result in prolongation of residence time and, therefore, increased concentrations in the circulation. It is necessary in the diagnosis and treatment of hyperlipidemia to assess the plasma concentrations of triglycerides, and it is important to establish recommendations for reliable triglyceride measurement. For the past several years, the National Cholesterol Education Program (NCEP) Working Group on Lipoprotein Measurement has been developing recommendations for triglyceride and low-density lipoprotein(LDL)-and high-density lipoprotein(HDL)-cholesterol measurement. 4 The Working Group’s recommendations for triglyceride measurement are summarized in this paper.