The ameliorating effect of the saponin rich fraction (SRF) prepared from the roots extract of Platycodon grandiflorum (Campanulaceae) on the scopolamine-induced cognitive dysfunction in mice were investigated by way of Moris water maze task. The mice with repeated oral administration of the SRF for four weeks showed markedly reduced the swimming time and swimming distance to reach the platform as well as the increase of number of crossing the platform on the Moris water maze task performed after scopolamine intoxication. The results suggest that SRF obtained from the roots extract of P. grandiflorum exert a cognitive enhancing effect on scopolamine-induced memory impairment in mice.