The effects of the nitrate to ammonium ratio on the growth and production of ginseng saponin (secondary metabolite) and polysaccharide (primary metabolite) by suspension cultures of Panax quinquefolium strain Q91625 were investigated at a total initial nitrogen (N) level of 60 mM in 250 ml Erlenmeyer flasks. A higher growth rate and greater final cell mass were obtained at a higher ratio of nitrate to ammonium. The biosyntheses of ginseng saponin and polysaccharide were also affected by the ratio of NO3-/NH4+, and ammonium was unfavourable to metabolite formation. The maximum production of saponin and polysaccharide was achieved when nitrate was used as the sole N source. The effect of total initial N (within 20-80 mM) on the cell cultures was also studied with NO3-/NH4+ ratios of 1:0 and 2:1. The final dry cell weight was similar throughout except that it was relatively low with 80 mM total N amount with a NO3-/NH4+ ratio of 2:1. The maximum production of ginseng saponin and polysaccharide obtained was 1.5 g/l (at an initial N level of 40 mM and a NO3-/NH4+ ratio of 1:0) and 2.19 g/l (at an initial N of 40 mM with a NO3-/NH4+ ratio of 2:1), respectively.