Signs and symptoms of volume overload is a common feature in patients presenting with acute heart failure syndromes. Management of volume overload, or congestion, is an important goal of therapy. Despite the importance of volume overload management, the precise causes have not been fully elucidated. The authors review possible explanatory models of volume overload and reflect on recent insights from acute heart failure syndromes clinical trials and registries. Congest Heart Fail. 2010;16(4)( suppl 1):S1–S6. ©2010 Wiley Periodicals, Inc.