The effect of ginsenoside (GS) from Panax ginseng on basal and nitro-L-arginine suppressed nitric oxide (NO) production was studied in rat kidney. NO production was determined by conversion to [(14)^C]-L citrulline from [(14)^C]-L-arginine both in whole kidney and three renal segments; glomerulus, cortex excluding glomerulus (cortex-) and medulla. Nitro-L-arginine (total dose of 30 ㎎/㎏/3 days, i.p.) significantly reduced NO production in whole kidney, which was prevented by GS pretreatment (30 ㎎/㎏/3 days, i.p.). Relative high dose of GS (120 ㎎/㎏/4 days, i.p.) selectively increased NO production in glomerulus and cortex-. Protein content, on wet weight basis, in cortex- and glomerular DNA content were significantly reduced by GS. Our results confirm the existence of constitutive nitric oxide synthase in kidney and it seems that target nephron segment for volume expansion due to GS` NO-mediated vasodilation and for NO production stimulated by GS is cortex including glomerulus.