We correlated the adenine nucleotide (AN) levels and energy charge (EC) at the end of a transient oxidative exposure to the delayed death of neuronal cells. When wild-type (WT) or Bcl-2-overexpressing (BCL-2) human neuroblastoma cells (Paju) were exposed to 250 µM H₂O₂ for 60 min, the EC of WT cells was unchanged, but that of BCL-2 cells decreased from 0.91 ± 0.03 to 0.67 ± 0.02. Depletion of ANs was significantly greater in BCL-2 (66.7 ± 2%) than in WT (38.8 ± 2%) cells. Proliferation of both lines decreased, averaging 63 ± 17% of control by 48 h. Exposure to 5 mM H₂O₂ caused no further change in ANs in BCL-2 cells but in WT cells decreased the EC to 0.45 ± 0.08 and depleted ANs to 41 ± 9% of control; after 24 h, WT cells became pyknotic and showed DNA fragmentation but no chromatin condensation, whereas BCL-2 cells died by delayed necrosis. After 10 mM H₂O₂, EC dropped to 0.15 ± 0.1, and both lines were acutely killed. The EC after an oxidative insult correlated well with further growth of both cell lines. A significant decline in EC led to delayed death. Bcl-2 did not protect against the fall in EC or AN depletion, but, although survival was not improved, the mechanism of death appeared to be different.