A new dammarane-type triterpene ketone, panaxadione, was isolated from the seeds of Panax ginseng C. A. MEYER (Araliaceae) together with two dammarane-type and lupane-type triterpenes, an aromatic oligoglycoside, three sterol glycosides, and three dammarane-type triterpene oligoglycosides (ginsenosides Rd, Re, and Rg(2)). The structure of a new compound was elucidated on the basis of physicochemical evidence. The relative contents of major ginsenosides in the seeds were compared with those of the flesh parts of young and mature fruits.