Investigation has been made into the action of glucono-delta-lactone on living cells of Pichia polymorpha in relation to the uptake of D-(U-14C)glucose, and the incorporation of (2-14C) uracil and L-(U-14C) threonine into RNA and protein respectively. Other factors such as the action of glucono-delta-lactone on cell morphology and on enzymic synthesis have also been studied. The action of this compound on beta-glucanase has been found to take place in the hydrolytic power and not in the synthesis.