Reduction in rehospitalization is an outcome measure used to evaluate home care services, especially in Outcome Based Quality Management using OASIS data; however, practitioners and managers must carefully analyze the reasons patients return to the hospital. This study examines events leading to rehospitalization of patients with CHF, whether it is possible to determine upon admission which patients are at risk, and whether the readmissions were necessary and/or preventable. Among the study's important findings are that half of the patients developed a new problem that required the rehospitalization. This and other research outcomes should be considered when analyzing adverse event reports.