The aim of the study was to verify whether the bioimpedance vector analysis (BIVA) could be a valid methodology to assess the fluid overload, whether there was a correlation between brain natriuretic peptide (BNP) and the fluid overload detected by BIVA, and whether this technique could be a valid guide in the management of the therapy in patients with acute decompensated heart failure (ADHF). A total of 51 patients arriving to the emergency department of the University Hospital Sant’Andrea (Rome, Italy) from December 2008 to April 2009 were enrolled. Hydration state, BNP, and caval index were evaluated at admission in the emergency department, at 24 and 72 hours, and at discharge. Vascular pedicle width was evaluated at admission and at discharge. BIVA values were correlated with BNP levels. A follow-up by phone at 3 months was performed. ADHF patients showed higher values of hydration state compared with controls. In ADHF patients, the difference between t 0 and t 72 BIVA mean values (P<.001) and between t 0 and discharge BIVA mean value (P<.0001) was statistically significant. Vascular pedicle width in ADHF patients showed a statistically significant difference (P<.0004) in compared with vascular pedicle width in controls. Congest Heart Fail. 2010;16(4)(suppl 1):S56–S61. ©2010 Wiley Periodicals, Inc.