Total extracts of ginseng (the root of Panax ginseng C. A. Meyer ) and saponin and polysaccharide fractions have been the main products used to investigate novel effects of ginseng over the last five decades. However, the differences if any between the pharmacological effects of total extract and saponin and polysaccharide fractions are largely unknown. In this study, we compared their effects on influenza A virus infection. Mice received total extract of Korean red ginseng (RG), and polysaccharide and saponin fractions of Korean RG, orally for 14 d prior to influenza A virus infection. Seventy eight percent of mice infected with 2× the 50% lethal dose (LD₅₀) of virus survived when administered the polysaccharide fraction, compared to 67%, 56% and 17% when administered total extract, saponin fraction and phosphate-buffered saline (PBS), respectively. Moreover, body weight loss in mice given the polysaccharide fraction was significantly reduced while there was mild reduction in body weight loss in that receiving saponin fraction or total extract when mice were infected with 0.2× or 0.5×LD₅₀ of virus. We also confirmed that the polysaccharide fraction was most effective in reducing the accumulation of tumor necrosis factor alpha (TNF-α)/inducible nitric oxide synthase (iNOS)-producing dendritic cells (tipDCs) in the mouse lungs. Our results indicate that the polysaccharides of RG have a pronounced beneficial effect on the symptoms of influenza virus infection.