Lipase (Triglycerol Acylhydrolase, EC 3.1.1.3), which is present in the grain of both rice and barley, catalyzes the hydrolysis of triglycerides at a lipid-water interface to yield free fatty acids (FFA). Triglycerides are the major lipid class in cereals. In barley, little FFA are present prior to germination. An increase in lipase activity of barley during germination of barley has been documented by a number of researchers. FFA liberated during germination are primarily metabolized by the beta-oxidation sequence, which is of physiological significance in terms of both energy production and sugar synthesis. However, it is the small amount of lipid not metabolized through these pathways that is of primary technological significance to the maltster and brewer. The link between lipase and oxidative rancidity of milled products is well documented. In brewing, FFA are generally associated with negative effects, including reduced head retention and the formation of stale/off-flavor aldehydes through oxidation of unsaturated FFA. The objective of this research was to determine the survival/stability of barley and rice lipase during mashing. All barley, malt and rice samples were obtained from commercial sources. Harrington and Robust barley were utilized in studies on the development/stability of lipase activity during malting and mashing. Micro-malting was conducted for up to five days at 16°C and 45% moisture. Green malt samples were freeze-dried prior to analysis. For mashing studies, a grist to water ratio of 1:4.3 was used. Wort was separated from the spent grain by centrifugation at specific time intervals. The spent grain was immediately frozen with liquid nitrogen and freeze-dried. Lipase activity determinations were conducted on the freeze-dried spent grains. Lipase activity was determined by a cupric acetate colorimetric method, utilizing triolein (emulsified with 10% gum arabic) as the substrate. Barley samples were found to contain 13-16 units/g lipase, and activity increased approximately 2-fold over five days of germination. Kilning reduced activity by only 10%. Lipase in milled brewers rice was 25-45% (3.7-6.0 units/g) of that present in barley. Malt lipase, found in the insoluble portion of the mash, appeared to be quite thermal stable. Activity was virtually unchanged following 100 minutes during which the temperature had been raised from 42°C to 67°C. Activity was found to decline by approximately 40% when the temperature was held at 74°C for 20 min. Results of this study suggest hydrolysis of triglycerides, and liberation of FFA, may continue through much of the mash.