Total saponins and ether extracts of red and white ginseng were obtained and their effects on blood pressure in cat and their histamine liberating activities in rabbits were measured. 1) Ether extract of red ginseng showed a transient hypotensive effect and subsequently showed a remarkable and persistent hypotensive effect, whereas other three fractions, such as saponin fractions of red and white ginseng and ether extract of white ginseng showed only a initial transient hypotensive effects. 2) Histamine levels liberated into blood after administration of each fractions measured by the bioassay with guinea pig ileum. Ether extract of red ginseng immediately increased histamine contents in plasma but the histamine levels decreased to normal level within 10min in spite of decreased blood pressure was sustained. Although white ginseng saponin lowered blood pressure immediately when it is administered, histamine release was observed after 10min. The results suggest that hypotensive effects of ginseng seems to have no correlation with the histamine liberating activity. Ginseng appears to show hypotensive effect via some other mechanisms.