I describe an enzymatic method for determining serum triglycerides (triacylglycerols). The triglycerides are hydrolyzed by a mixture of lipase and esterase. The glycerol released is determined by kinetic fixed-time analysis, with use of glycerol kinase, pyruvate kinase, and lactate dehydrogenase. Through addition of the competitive inhibitor ATP the Michaelis constant of pyruvate kinase is apparently increased, considerably extending the linearity of the assay. There is no need for serum blanks or reagent blanks. The method has been adapted to a centrifugal analyzer (the ENI GEMSAEC). It yields satisfactory results with regard to precision, accuracy, and insensitivity to interferences