The in vivo administration of extract of the roots of Panax ginseng C. A. MEYER increased the incorporation rate of labeled precursors into liver nuclear RNA at 4 hr and into cytoplasmic polysomal RNA at 5.5-6.0 hr after a single dose intraperitoneal injection in a rat. The incorporation rate was directly dependent on the amount of a fraction obtained by partial purification. The increased specific radioactivity of the liver RNA is not due to the change in the pool size of endogenous acid-soluble nucleotides.