Ethanol and water extracts of white and fermented ginseng were prepared and their ginsenoside composition and antioxidant effects were assessed. The main ginsenosides in white ginseng were $Rb_1$ > Re > $Rg_1$, and those in fermented ginseng were $Rb_2+Rb_3$ > Rd > $Rg_1$. Ginsenosides Rd and $Rg_3$ in fermented ginseng were enriched 11 and 58 times, respectively, over that in white ginseng through fermentation with five Bacillus spp. The greatest levels of 2-deoxyribose and superoxide anion dismutase-like activities were found in 50% ethanol extracts of fermented ginseng. Thus, these data suggest that white ginseng has the greatest free radical scavenging activity and that fermented ginseng has the highest antioxidant activity.