Abstract: AIM:To study how plasma arginine-vasopressin (AVP) and urinary aquaporin-2 (AQP2) are related with left ventricular ejection fraction (LVEF) and hyponatremia in patients with congestive heart failure (CHF). METHODS: Double antibody sandwich enzyme-linked immunosorbent assay (ELISA) and radioimmunoassay synchronous detection were conducted to examine and compare urine AQP2 and plasma AVP levels as well as serum sodium and LVEF in 265 CHF patients and 92 healthy subjects. RESULTS: The levels of plasma AVP and urinary AQP2 in CHF patients were higher than those in healthy controls and serum sodium concentration and LVEF were negatively correlated. CONCLUSION: Compared with AVP, AQP2 can better reflect water metabolism disorder and urinary AQP2 may be used as a bedside index for detection of severity of heart failure and imbalance of water and sodium.