A procedure of3H-radio-labeling synthesis for the dammarane triterpene glycosides of Korean ginseng was established by using the ginsenoside Rg1 as starting material. The protons in C11 and C13 of the aglycone moiety of the glycoside were exchanged with tritium by keto-enol tautomerization of 12-keto-ginsenoside Rg1 which was prepared by partial acetylation, Sarett oxidation and saponification, producing nona-acetate, nonaside Rg1. The acetyl-ketone and 12-keto-derivative of ginsenotritiated ketone was reduced by metallic sodium and isopropanol to produce the end product3H-ginsenoside Rg1 with 3% radio-chemical recovery in one experiment.