Two inbred lines of rye (Secale cereale L), the kernels of which displayed a very low level of β-amylase activity (1-3% of the levels generally found in rye), were investigated in comparison with a third normal line. An anti-wheat β-amylase immune serum which cross-reacted with the rye enzyme was used in this study.The anti-wheat β-amylase immune serum absorbed the β-amylase activity in the three lines which were investigated. Comparably small amounts of enzymatic antigen corresponded to the small levels of activity detected in the enzyme-deficient lines. The three inbred lines were equally able to germinate. One of the enzyme-deficient lines was further investigated and neither the level of activity nor the amount of enzymatic antigen were notably changed upon germination.The results indicate that the reduced activity is due neither to the presence of an inhibitor nor to the production of inactive enzymes. Germination can proceed normally without late production of β-amylase.