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Glucose greatly increased total free fatty acid (FFA) esterification by Ehrlich ascites tumor cells. However, the FFA concentration of the cells was not altered. Less exogenous FFA was oxidized to CO2 at any given extracellular FFA:albumin molar ratio when glucose was available, but increasing amounts of radioactive CO2 were produced as the FFA:albumin molar ratio was raised, even in the presence of glucose. It is suggested that glucose, by providing either energy or an excess of triose acceptor for fatty acid esterification, stimulated FFA uptake only indirectly, by increasing the utilization of FFA subsequent to initial uptake from the medium, i.e., by increasing the turnover rate of the cellular FFA pool.Availability of glucose decreased the oxidation of endogenous lipid radioactivity and the depletion of endogenous lipid ester radioactivity. Most of the radioactivity utilized was derived from phospholipids, and depletion of phospholipid radioactivity was spared when glucose was available. Depletion of cellular total lipid ester also was spared in the presence of glucose.Availability of FFA did not decrease total glucose uptake or its oxidation to CO2. Glucose utilization by these cells appears not to be regulated by FFA availability in the manner that Randle and coworkers described for muscle.