Background: Adherence to heart failure therapy is important in reducing morbidity and mortality over the course of the disease process. The aim of this study was to examine factors associated with non-adherence to warfarin in chronic heart failure patients. Methods: Eighty patients receiving warfarin therapy in 2002 were included. Adherence was defined as maintenance of international normalized ratio (INR) between 2 and 3.5 and keeping scheduled appointments for INR checks at least 75% of the time. Clinical variables examined included age, gender, race, insurance, left ventricular ejection fraction (LVEF), etiology, New York heart association (NYHA) class, comorbidities, smoking, and alcohol use. Results: Of 80 patients studied, 59 were male with mean age (± standard deviation) 52 ± 13 years, 24 had ischemic etiology with mean LVEF of 24% ± 9%. Non-adherence was associated with tobacco use, odds ratio of 6.5 (p < 0.01). Ischemic etiology was associated with adherence, odds ratio of 4.5 (p < 0.01). Non-adherent patients were more likely to be insured with Medicare/Medicaid (p = 0.04) and have better NYHA class (p = 0.04). Adherence positively correlated with older age and lower LVEF, and negatively correlated with number of hospitalizations (p<0.01 for all). In a multiple regression model, patients with improvement in LVEF had decreased adherence over the year (p<0.01). Conclusions: The profile of heart failure patients who demonstrated non-adherence to warfarin therapy included younger age, nonischemic etiology, better NYHA class, smoking, insurance with Medicare/Medicaid and improved LVEF over the study. Measures targeting these patients may result in improved adherence to other pharmacologic treatments of heart failure. © 2008 Wiley Periodicals, Inc.