In order to find out the inhibitors of acetic acid fermentation in Korean ginseng (Panax Sin son C. A. Meyer), total aglycone, panaxadiol, panaxadiol, oleanolic acid and ${eta}$ -sitosterol were added to the basal medium, respectively, and a surface culture was carried out at 30$^{circ}C$. The results were as follows: 1 . Saponins lost their activity to inhibit the acetic acid fermentation by hydrolysis. 2 Panaxadiol inhibited slightly, and the degree of inhibition was about 1/300 of that of free saponins. 3. Panaxadiol and oleanolic acid inhibited silighly similar to total aglycone. 4. Acetic acid fermentation was stimulated at the early stage when ${eta}$-sitosterol was added to the media below the level of 0.000815%. But the fermentation was inhibited when media contained it more than that media 5. An over-oxidation of acetic acid was observed when the media contained total aglycone. panaxadiol, panaxatriol, oleanolic acid and ${eta}$-sitosterol, respectively, while the media which contained sucrose, ginseng extracts ginseng saponins was shown not to be over-oxidized.