The proteolytic activities during rye (Secale cereale L. 'Humbolt') grain germination were monitored using in-solution methods and one- and two-dimensional PAGE with gels that contained incorporated substrate proteins. The total proteolytic activity increased during the first three days of germination, but not after that. The proteinase activity was measured at pH 3.8, 6.0, and 8.0 in the presence and absence of class-specific proteinase inhibitors. This indicated that enzymes from all four proteinase classes were present during the germination process. Germinated rye grain contained mainly aspartic and cysteine proteinase activities that are especially active at pH 3.8. Serine- and metallo-proteinases were less abundant. Overall, the pattern of hydrolysis was very similar to that observed during barley and wheat germination.