BACKGROUND: Ketamine, a dissociative anesthetic, was known to be beneficial in reducing neuronal or astroglial damage by anoxic or ischemic insults. Detection of DNA fragments in situ using the terminal deoxyribonucleotidyl transferase (TDT)-mediated dUTP-digoxigenin nick end labelling (TUNEL) assay is recently applied to investigate active cell death. Therefore, we tried to investigate the relationship of ketamine effect with DNA breakdown in the condition of low ATP. METHODS: Experimetal protocols are as follows: Astrocytoma cells were harvested and plated to chamber slides. Then experimental cells were divided to four groups as control group, iodoacetate (IAA)/carbonylcyanide m-chlorophenylhydrazone (CCCP) 1.5 mM/20 micrometer treated group, and IAA/ CCCP with ketamine 1 mM or 0.1 mM. In situ labelling of fragmented DNA was conducted with commercially available kits (In situ cell death detection kit, Boehringer Mannheim). Stained cells were observed by the use of light microscope. RESULTS: TUNEL-positive reaction appeared in energy depleted astrocytes. However, TUNEL-positive cells were not observed after perfusion with iodoacetate/CCCP and ketamine 0.1 mM or 1.0 mM together. CONCLUSIONS: We report here that in vitro addition of ketamine 0.1 mM or 1 mM protected DNA breakdown of astrocytes from energy depletion. These results suggest that ketamine may have potential effect in preventing ischemic damage in clinical setting.