Incubation of yeast cells for 21 hours in solutions of certain sugars and polyols produces cells capable of forming CO2 from glucose at a high rate and without an initial lag as compared to cells starved by incubation in water. Other sugars and other compounds, including amino acids, purines and pyrimidines, and organic and inorganic salts, were ineffective or reduced CO2 production. Readily metabolized sugars were effective at concentrations of 0.001 M, poorly metabolized sugars required higher concentration, and non-metabolized sugars were ineffective. However, mannitol and sorbitol, non-metabolized polyols structurally related to utilized sugars, were effective. Alcohols and polyols added to the cells after incubation in water overcame the lag period. Sugars produced a persistent change, acted faster than polyols, and were more effective in the presence of non-effective compounds. Readily utilized sugars at high concentrations reduced cell viability and the decarboxylase- and CO2-producing capacities of cell extracts. The nicotinamide adenine dinucleotide contents of extracts did not indicate deficiencies, and differences in adenosine triphosphate contents appeared not to be significant. The data may be interpreted as evidence for an effect by the sugars and polyols primarily upon intracellular membranes.