The effect of anaerobiosis, imposed during germination of ‘Calypso’ cucumber (Cucumis sativas L.) seeds, was studied. Anaerobic conditions inhibited reserve mobilization from the cotyledons and dry weight gain by the embryonic axis. Within the embryonic axis, lipid degradation was stopped and use of all readily metabolizable carbohydrate reserves was strongly stimulated. By 48 hr of exposure to an anaerobic environment, the axis was nearly depleted of endogenous carbohydrate reserves. Aerobically germinating seeds accumulated a massive concentration of hexose sugars within the axis during the same time period. Thus, growth inhibition within cucumber seeds during anaerobiosis may result in part from carbohydrate deprivation of the embryonic axis.