Cognitive dysfunction is a frequent finding among older patients with left ventricular systolic dysfunction; however, the clinical outcomes of such a finding are unknown. Also, disability is a common condition in heart failure, poorly responding to commonly used cardiovascular medications. The association between cognitive dysfunction and disability was assessed in 1583 patients with heart failure, but without cerebrovascular disease, previous stroke, or Alzheimer's disease, who were enrolled during 2 years of a multicentre pharmacoepidemiology survey. The association between groups of variables (demographics, comorbid conditions, medications, and objective tests, including the Hodkinson abbreviated mental test) and functional disability (as indicated by need for intensive assistance in at least one of Katz' activities of daily living) was first analysed using separate age and sex adjusted logistic regression models. Those variables, significant at a p<0.1 level in these models, were simultaneously entered into an age and sex adjusted summary regression model. Among 1583 patients suitable for analysis, cognitive dysfunction (as detected by abbreviated mental test score <7) was detected in 265/461 disabled patients, and in 150/1122 independent subjects (p<0.0001). According to logistic regression analysis, cognitive dysfunction was associated with disability (OR=6.49; 95% CI=4.39-9.59) after adjusting for potential confounders.Thus, cognitive dysfunction in patients with heart failure is independently associated with disability, which currently represents an overwhelming medical and financial problem to patients, caregivers, and public health services. As early recognition and treatment of low cardiac output states might reverse cognitive dysfunction, cost effective treatment for heart failure should include systematic diagnostic and therapeutic approaches to cognitive dysfunction.