A study 6was Planned to see if administration of ginseng extract has any influence upon cerebral nucleic acid content of mice. Thirty male mice (body weight: 18 ~ 20 gm) were divided into the ginseng and the saline groups. Once a day for S days they received subcutaneously 0.05 ml/10 gm body weight of ginseng extract solution (4 mg of ginseng alcohol extract in 1 ml of saline), and the same amount of saline, respectively. On the 5th experimental day, all animals were sacrificed 2 hours after the last medication and their cerebral tissue was removed. Cerebral RNA and DNA contents were measured using the chemical method of Schmidt-Thannhauser-Schneider. Following results were obtained: 1. Cerebral RNA and DNA contents were significantly higher in the hippocampal group than in the saline group. 2. The RNA/DNA ratio was lower in the ginseng group compared with that in the saline group, because the cerebral DNA increased more remarkably than the RNA did following administration of ginseng. The ginseng is inferred to augment cerebral RNA and DNA content of mice.