The study uses residents of the Worcester (MA) metropolitan area (1990 census 437,000) and examines changes over time in these and additional outcomes for patients with validated heart failure during 1995 and 2000. Complimenting the hospital surveillance of heart failure, newly diagnosed cases of heart failure occurring in members of the largest HMO in Central Massachusetts during 1995 and 2000 will be identified and monitored over time. To accomplish the study objectives, the medical records of residents of the Worcester metropolitan area hospitalized with a discharge diagnosis of heart failure and related diagnostic rubrics will be individually reviewed and validated according to pre-established diagnostic criteria. The use of traditional criteria for heart failure as well as development of new criteria for the epidemiological study of heart failure will be an important focus of this observational study. Records for additional hospitalizations and death certificates will be reviewed to examine trends in long-term survival of discharged hospital patients through the year 2005.