The aim of this study is to purify and characterize the multiple endogenous protease inhibiting compounds that occur in barley and malt. These compounds play important roles in malting and brewing by suppressing the activities of the malt cysteine endoproteinases, the main enzymes involved in forming wort soluble protein. Barley and malt extracts both contain multiple inhibitors that were detected after the extracts were boiled and separated chromatographically. Extracts that were not boiled showed no inhibitory activity, indicating that the inhibitors are tightly bound to compounds that render them inactive until they are removed by heating. Two proteins have been purified to homogeneity and characterized. One, a 10 kDa protein, is identical to a protein previously named ‘lipid transfer protein 1' or ‘probable amylase/protease inhibitor’ (LTP1-PAPI). It is commercially important because it improves the formation and strength of beer foam. The other, LTP-2 is a small 7 kDa protein. We are presently purifying and characterizing a malt protein that inhibits the activity of the papaya cysteine class proteinase called papain and of some papain-like proteinases that occur in green malt. Some of these inhibitory proteins are obviously important for controlling protein solubilization and foam stability during malting and brewing. Delineating how and where they function will make it possible to manipulate them to produce improved malting barleys.