The activity of CVT-E002, an aqueous extract containing mainly oligosaccharides andpolysaccharides from North American ginseng (Panax quinquefolium), as an immunoboosteron murine spleen cells and peritoneal macrophages, was studied in-vitro. CVT-E002 stimulatedthe proliferation of normal mouse spleen cells, of which the major responding subpopulationwas identified as B lymphocytes. CVT-E002 also activated peritoneal exudate macrophagesleading to enhanced interleukin-1 (IL-1), interleukin-6 (IL-6), tumour necrosis factor-a (TNF-a)and nitric oxide (NO) production. In addition, CVT-E002 stimulated in-vivo immunoglobulin G(IgG) production in treated mice. These results identify some of the immunomodulatingactivities of CVT-E002 and suggest its use clinically for the modulation of immune responses.