This study was carried out to examine the effects of ethanol extract (EXPG) and saponin (SAP) from Platycodon grandiflorum on scopolamine-induced amnesia in mice. Fifty male ICR mice were assigned to five groups--normal (normal diet + saline), control (normal diet + scopolamine), EXPG 0.2% (normal diet + 0.2% EXPG + scopolamine), EXPG 0.5% (normal diet + 0.5% EXPG + scopolamine), and SAP 0.02% (normal diet + 0.02% SAP + scopolamine)--and fed each diet ad libitum. After 4 weeks of feeding the appropriate diet, scopolamine (1 mg/kg, i.p.) was given to mice 45 minutes before the passive avoidance and Morris water maze tasks. Both the EXPG groups and the SAP group exhibited significant amelioration of scopolamine-induced amnesia as measured in both the passive avoidance task and the Morris water maze task. Moreover, acetylcholinesterase (AChE) activity and the levels of thiobarbituric acid-reactive substance (TBARS) in the serum and brain of the EXPG groups were lower than those of the control group. These results suggest that EXPG may improve the cognitive deficit caused by scopolamine and that these effects might be due to EXPG mediated by inhibition of AChE activity and inhibition of TBARS.