Triacylglycerols secreted by liver and carried by very low density lipoprotein (VLDL) are hydrolysed in circulation by lipoprotein and hepatic lipases. These enzymes have been shown to have positional and fatty acid specificityin there were specificity in basal lipolysisin vivo, triacylglycerol compositionsofcirculatingandnewlysecretedVLDLwould be different. To study this we compared the composition of normal fasting VLDL triacylglycerol of Wistar rats to that obtained after blocking lipolysis by Triton WR1339, which increasedplasmaVLDL triacylglycerol concentrationabout in 2 h. .