AbstractThe stereochemical course of the hydrolysis of synthetic sn‐glycerol‐1‐palmitate‐2‐oleate‐3‐linoleate, sn‐glycerol‐1,2‐dipalmitate‐3‐oleate and their antipodes by pancreatic and milk lipoprotein lipase was investigated by thin layer and gas liquid chromatographies of the diacylglycerol intermediates. The enzymic hydrolyses were made with bile salts or lysolecithin in a 1∶1 molar ratio to the substrate as emulsifiers and were limited to short time intervals which minimized isomerization and the reversal of lipolysis. In all instances, the products of hydrolysis by lipoprotein lipase contained a marked preponderance of the 2,3‐diacylglycerols, while the composition of the diacylglycerol intermediates in the products of pancreatic lipase varied with the nature of the fatty acid in the 1 and 3 positions of the triacylglycerol molecule. Pancreatic lipase, but not lipoprotein lipase, gave a preferential release of unsaturated fatty acids. The above results are similar to those obtained with radioactive trioleoylglycerol and conventional stereospecific analyses and suggest that lipoprotein lipase may favor attack on the sn‐1 position. It is hypothesized that the small amounts of the 1,2‐diacylglycerols present may have arisen from a reversal of lipolysis also catalyzed by this enzyme.