Panax vietnamensis Ha et Grushv. is an important source of majonoside R2, a dammarane saponin with an ocotillol side-chain, which is an interesting pharmacological active compound. Thirty-one transformed root lines were obtained after the inoculation of in vitro shoot explants of P. vietnamensis with Rhizobium rhizogenes ATCC 15834 strain. The transgenic nature of the hairy roots was confirmed by PCR amplification. The established hairy root lines displayed four morphological phenotypes when cultured on hormone-free medium. Most of the cultures showed the characteristic traits of hairy roots with primary roots, an extensive lateral branching and rapid growth. Kinetic growth of these hairy root lines was measured for 90 days and a biomass production of about 10 g L-1 fresh weight was obtained. The ginsenoside content of hairy roots was identified by LC-MS and compared with that of 6 year-old rhizomes of P. vietnamensis. Majonoside R2 was recovered in trace amounts, but other ocotillol saponins, pseudoginsenoside F11 and vinaginsenoside R1, were recovered in larger proportions. These results indicate that hairy roots of P. vietnamensis present an interesting potential to produce ginsenosides and, in particular, ocotillol saponins.