A highly dampened train of oscillations may be obtained from aerobic suspensions of a hyperdiploid strain of Ehrlich ascites tumor cells, provided the cells are incubated until endogenous substrates just have been depleted. Several intermediates were measured in such oscillating systems and their interrelationships studied. These data were compatible with the concept of glycolytic control by intermediates at the levels of phosphofructokinase and hexokinase and incompatible with the concept of control of glycolysis by mitochondrial sequestering of ATP. On the other hand, they were consonant with the concept of respiratory control mediated by excess mitochondrial ATP, as well as with other possible mechanisms. They further suggested that citrate may act as a dampener, normally preventing oscillations of phosphofructokinase caused by rapid changes in mononucleotide levels; that hexokinase was inhibited by glucose-6-phosphate but ultimately controlled by some other factor; and that the α-GP oxidase was activated briefly but normally remains inactive in these cells.