Cognitive impairment has seldom been investigated in patients with chronic heart failure (CHF). The authors' aim was to assess the prevalence and determinants of cognitive impairment in patients hospitalized for CHF decompensation. The authors prospectively performed the Folstein Mini-Mental State Examination (MMSE) and completed a standardized questionnaire for cerebrovascular accidents (CVA) and transient ischemic attacks (TIA) in patients hospitalized for CHF decompensation during a 3-month period. A total of 83 patients were studied: 15 had a history of CVA or TIA, 51 (61%) had an MMSE score < or = 28 (or < or = 26 if schooling < or = 8 years), and 26 (31%) had an MMSE score <24. Factors associated with an MMSE score <24 were atrial fibrillation/flutter (odds ratio [OR], 8.1; 95% confidence interval [CI], 1.9-34.6), New York Heart Association functional class IV (OR, 4.1; CI, 1.0-16.4), and schooling >8 years (OR, 0.2; CI, 0.0-0.8). Adjusting for history of CVA or TIA or excluding patients with a history of CVA or TIA did not affect the findings. Cognitive impairment is frequent in patients hospitalized for CHF decompensation whether or not they have a past history of CVA or TIA. The severity of cognitive impairment parallels that of CHF. The question of whether this cognitive impairment decreases adherence to treatment and contributes to a worse outcome in CHF patients should be explored.