The intracellular concentrations of adenylates and the value of the adenylate energy charge in Schizosaccharomyces pombe have been determined. Dilution of extracts before enzymically converting AMP and ADP to ATP was necessary for the quantitative measurement of all three adenylates. Using trichloroacetic acid or perchloric acid extracts of exponentially growing cultures, the energy charge was calculated to be 0.8 to 0.9; the value rose to about 0.95 in the stationary phase of growth. Lower energy charge values (0.6 to 0.64) were obtained using chloroform extracts. During the last 2.5 h of a 4 h treatment of an exponentially growing culture with 2′-deoxyadenosine, and during the induced synchronous growth that followed subsequent removal of the inhibitor, the pool sizes of all three adenylates oscillated. Minimal ATP/ADP ratios (and energy charge values) occurred concurrently with maximal rates of respiration that were relatively insensitive to stimulation by carbonyl cyanide m-chlorophenylhydrazone. Cultures not treated with 2′-deoxyadenosine but centrifuged and resuspended in fresh medium, showed a transient extensive increase in the ATP/ADP ratio 1 to 2 h after resuspension. However, rates of O2 uptake, in the absence or presence of carbonyl cyanide-m-chlorophenylhydrazone, increased smoothly throughout this period. The results suggest that, in 2′-deoxyadenosine-induced synchronous growth, respiration rates may be controlled by the intracellular ATP/ADP ratio, and demonstrate that division synchrony is not induced by depletion of ATP pools.