The effects of the protein fraction of Panax ginseng on primary cultured chicken embryonic brain cells and DRG cultured with a deficient medium were studied. The protein fraction was further fractionated into four groups according to the molecular weight; larger than 10,000 dalton(fraction A), between 5,000 and 10,000 daltons(fraction B), between 1,000 and 5,000 daltons(fraction C), between 500 and 1,000 daltons(fraction D). All four protein fractions at the concentration of $100;{mu}g/ml$ significantly increased the number of the brain cells which promoted the neurite outgrowth. The activity of PDHC in the brain cells was elevated significantly by the protein fraction B at the concentration of $100;{mu}g/ml$. It was noted that $100;{mu}g/ml$ protein fraction C and D significantly enhanced the synthesis of protein in the brain cells. At the concentration of $100;{mu}g/ml$, the protein fraction B enhanced RNA synthesis and the protein fraction A significantly enhanced DNA synthesis in the brain cells. The protein fractions B, C, and D significantly promoted the neurite outgrowth of DRG at the concentration of $100;{mu}g/ml$.