Abstract: The effect of ginsenoside Rh₂,a constituent isolated from Panax ginseng C.A.Meyer,on the growth of tumor cells in vitro was investigated.The results showed that Rh₂ inhibitedthe growth of B₁₆ cells at the concentration of 10μg·ml^-1(IC₅₀:4.1μg·ml^-1).Rh₂ was found tosignificantly induce the activity of differentiation of B₁₆ cells at the concentration of 10μg·ml^-1 invitro。The melanin synthesis of Rh₂ in treated B₁₆ cells was increased.Morphologically,the Rh₂ induced B₁₆ cells turned to be epithelioid cells.B₁₆ cells became dendrite shaped morphologically athigher concentration of Rh₂.Flow cytometry demonstrated that the B₁₆ cells treated with Rh₂ wereblocked at G₁ phase.