BACKGROUND Psychologic dysfunction is common in patients with heart disease. Patients with end-stage cardiac failure have cognitive dysfunction that can affect their ability to comply with complex treatment regimes. The prevalence of cognitive dysfunction in patients with stable, moderately severe cardiac failure is not known. The purpose of this study was to evaluate the prevalence of memory dysfunction in that population. METHODS Twenty patients with previous myocardial infarction (MI), New York Heart Association class III or IV cardiac failure symptoms, and left ventricular ejection fraction (LVEF) <40% were studied. Twenty patients with previous MI, no heart failure symptoms, and LVEF >50% were studied as a control group. Memory function was assessed with the Rivermead Behavioural Memory Test and digit span test. Results were controlled for affective state and estimated premorbid intellectual function with the National Adult Reading Test. RESULTS Patients with cardiac failure performed as well as controls in the memory test (mean [95% confidence intervals] score 18.2 [16.5-19.9] versus 19.7 [18.1-21.4] points, P =.20) and digit span test (10.1 [9.2-11.0] versus 11.0 [9.9-12.2] points). Affective symptoms were more prevalent among patients with cardiac failure. Estimated premorbid intellectual function appeared poorer in patients with cardiac failure (reading test score 24 [7-36] versus 32 [11-46] points). Memory test outcomes were not significantly affected after adjustment for these variables. CONCLUSIONS Patients with prior MI and stable, moderately severe cardiac failure do not have significantly memory impairment. Memory dysfunction is not likely to interfere with rehabilitation or compliance with treatment regimes. Anxiety and depression, however, are relatively common in this group.