This study was performed to examine cognitive function in patients with end-stage heart failure, to identify possible cardiovascular factors associated with cognitive function, and to evaluate changes in cognitive function in a subgroup of patients who received heart transplantation. An extensive battery of neuropsychological tests were given to 62 patients with end-stage cardiac failure as part of their evaluation for cardiac transplantation. Most patients were consecutive referrals, not selected because of cognitive complaints. A small subgroup of transplanted (n = 7) and non-transplanted (n = 4) patients received a repeat neuropsychological examination. At initial examination, approximately 50% of the patients met criteria for impairment in reference to normal control values. Higher stroke volume index and cardiac index and lower right atrial pressure were correlated with better cognitive function. In the subgroup of patients re-examined, the transplanted patients demonstrated significantly improved cognitive function, whereas the non-transplanted subjects were unchanged. These data indicate that in patients with end-stage heart failure there is a high prevalence of impaired cognitive function which is related to measures of cardiovascular efficiency. Preliminary evidence suggests that these impairments may be partially ameliorated by cardiac transplantation.