Heart failure is a leading cause of hospitalization for adults in the United States. Patients hospitalized with acute decompensated heart failure (ADHF) face a substantial risk of in-hospital mortality and rehospitalization. Despite the large number of patients hospitalized and this substantial risk, data on these patients have been limited and there has been little effort to improve the quality of care for patients hospitalized with ADHF. The Acute Decompensated HEart Failure National REgistry (ADHERE(tm)) was designed to bridge this gap in knowledge and care by prospectively studying characteristics, management, and outcomes in a broad sample of patients hospitalized with ADHF. Participating community and university hospitals identified patients with a primary or secondary discharge diagnosis of heart failure and collected medical history, management, treatments, and health outcomes via secure web browser technology. As of July 2003, 65,180 patients have been enrolled from 263 hospitals. Initial data have provided important insights into the clinical characteristics, patterns of care, and outcomes of these patients. ADHERE documents significant delays in diagnosis and initiation of ADHF therapies as well as substantial under-use of evidence-based, guideline-recommended chronic heart failure therapies at hospital discharge. As such, there are substantial opportunities to improve the quality of care for ADHF patients in the nation's hospitals. The ADHERE Hospital Toolkit has been designed to provide hospital teams with effective proactive instruments to improve the quality of care for patients with ADHF. If successfully implemented, the improvements in short- and long-term clinical outcomes for ADHF patients are expected to be substantial.