In order to observe effects of ginseng extract on the incorporation of glucose-(U)-$^{14}C$ and Amino Acid mixture-$^{14}C$ into lipid and protein in rat brain, a methanol extract of the roots of dried ginseng was prepared. The extract was administered to rats in single dose of 5 mg in 0.5 ml of saline solution per body weight of 100g for 4 days, the control group was injected with 0.5ml of saline. The two groups were subdived into the feeding and the fasting (24 hours). After one hour following the final admin istration of ginseng extract and saline respectively, all animals were injected with $4;{mu}Ci$ of glucose-(U)-$^{14}C$ with 100 mg of D-glucose, or $4;{mu}Ci$ of amino acid mixture-$^{14}C$ with 20 mg of L-alanine, per body weight of 100g. Three hours later, the radioactivity of $^{14}C$-incorporporated into brain lipid and brain protein was measured with gas flow counter. The conversion rates of glucose or amino acid mixture into brain lipid were decreased in groups administered with ginseng than in the control groups in both feeding and fasting condition. The rates of glucose or amino mixture into brain protein were increased with administration of ginseng extract. These effects of ginseng extract were remarkable in the fasting groups.