It was planned to evaluate the influence of Panax Ginseng upon DNA synthesis of submandibular gland in mice by observing incorporation of [3H] thymidine into the tissue cells. Thirty male mice (body weight: 18 ~ 20 g) were divided equally into two groups. One group received every day (subcutaneously) 0. 05 ml/10 g body weight of ginseng extract(4 mg of ginseng alcohol extract in 1ml of saline), while !he other group received the same amount of saline, for 5 days. On the 5th experimental day, all animals received 1 μCi/g body weight of [3H] thymidine intraperitoneally 2 hours after the last medication. Five animals, at a time, of each group were sacrificed 1, 10, and 24 hours after [3H] thymidine administration, and the radioactivity of cells in their mandibular gland was measured autoradiographically in terms of the % number of radioactive cells in 1,000 tell counts (Radioactive Index, R.I.). It was found that the radioactive indices of mice that received ginseng were lower than the corresponding values of mice that received saline. The inference from the above result was that the ginseng suppressed DNA synthesis of cells in the mandibular gland.