In order to study specificity of pancreatic lipase, a number of synthetic triglycerides were hydrolyzed by the enzyme under an improved condition. The proportions of isomers of the derived mono- and diglycerides, and the fatty acid compositions of the derived free acids and monoglycerides were determined. The hydrolyzing rate of fatty acids in glycerides depended on the position esterified in the glycerol, carbon number of the acid, and structure of the glyceride. Positional specificity of the enzyme was markedly displayed for symmetrical triglyceridcs composed of long chain acids, but at somewhat lower rate for glycerides containing short chain or highly unsaturated acids.