This study was performed to determine the effect of dietary Na levels on plasma amino acid levels. Plasma amino acid levels were compared in 20 adult healthy women subjects who were given high Na diet (290.48 mEq/day : NaCl 17g) or low Na diet (51.26 mEq/day : NaCl 3g) for subsequent 6 days. Plasma essential amino acids levels were significantly decreased (36%) while plasma non-essential amino acids levels were significantly increased (22%) when subjects were given low Na diet (p＜0.001). Among essential amino acids, threonine was decreased (74%) significantly when subjects were given low Na diet (p＜0.01). Among nonessential amino acids, serine (49%), proline (20%) and aspartic acid (14%) were increased (p＜0.01), while arginine (48%) and glutamic acid (27%) were decreased (p＜0.001). In conclusion, dietary Na contents seemed to be an important factor to affect plasma amino acid levels. It would be appropriate to decrease the dietary Na intakes level considering the various clinical effects of dietary Na on the body fluid. For the patients who need low Na diet, it would be suggested that the level of dietary proteins should be carefully considered along with dietary Na manipulation. (Korean J Nutrition 37(2) : 108-114, 2004)