Research Objectives Heart failure (HF) is a common condition in persons older than 65 years. Existing literature indicated that hospital readmission rates after discharge for heart failure patients are immensely high. However, previous studies showed that almost half of the early hospital readmissions could be prevented. Moreover, Angiotensin-converting enzyme (ACE) inhibitor and Angiotensin receptor blocker (ARB) are the commonly used medications for heart failure patients to control blood pressure. Nevertheless, studies indicated that these two medications could also cause the risk of hospital readmission. Little studies examined the associations of medication use and hospital readmission of heart failure patients in Taiwan. This study aims to investigate the influence factors of hospital readmissions among heart failure patients in Taiwan. Study Design We collected the data from National Health Insurance (NHI) database during the period from year 2000 to 2006. Based on the rule of Bureau of National Health Insurance in Taiwan, the 14-day readmission is considered as a poor quality indicator. We categorized readmissions into 4 groups (14-day, 30-day, 180-day and over 180-day) and evaluated each group¡¦s demographic, hospital characteristics, medical resource utilization, Charlson Comorbidity Index and medication utilizations of ACE inhibitor and ARB. We conducted descriptive analyses by using chi-square and t tests and applied multivariate logistic regression analyses to estimate the probabilities of hospital readmissions of heart failure patients. Population Studied Patients aged 50 or older with heart failure were identified based on the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). Principle Findings Among 1920 heart failure patients, 19.9% of them were readmitted within 14 days, 7.6% were readmitted within 30 days and 26% were readmitted within 180 days. The medical resource utilizations such as average inpatients cost per patient, average outpatients cost per patient, total medical cost, average of inpatients times per patient and average of outpatients times per patient were significantly higher in patients with readmissions than those without readmission. Age, Charlson Comorbidity Index, patients who had been treated with ACE inhibitors and patients who had been treated with ARB were significantly affected the probabilities of readmissions. Conclusion The heart failure patients with readmissions had significantly higher medical resource utilizations than those without readmission. The medication uses of ACE inhibitors or ARB were significantly affected the probabilities of hospital readmissions. By understanding more about the influence factors of readmissions among heart failure patients, we may provide continue improvements of quality of care and reduce unnecessary medical costs. This study results provide useful reference for policy-makers to establish effective disease management program and appropriate health care financing arrangement in the future.