As a part of efforts to elucidate the influence of Panax Ginseng upon nucleic acid content of various tissues, a study was carried out which measured RNA and DNA contents of bone marrow following administration of ginseng. Thirty male rats (body weight: 180 ~ 230 gm) were equally divided into a ginseng and a saline group. Once a day for 5 days they received subcutaneously 0.5 m1/100 gm body weight 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 the bone marrow of one femur was removed. RNA and DNA contents of the bone marrow were measured using the chemical method of Schmidt Thannhauser-Schneider. Results obtained were as follows 1. RNA and DNA contents of the bone r arrow were significantly higher in the ginseng group than in the saline group. 2. RNA/DNA ratio of the bone marrow was also much higher in the ginseng group than in the saline group. The ginseng is inferred to augment RNA and DA contents, and also raise RNA/DNA ratio of the bone marrow in rats.