Systolic load elevation during exercise prolongs left ventricular (LV) relaxation, compromises filling, and raises end-diastolic pressure, leading to reduced exercise tolerance. The aim of this study was to test the hypothesis that the hypertensive response to exercise is exaggerated in patients with diastolic heart failure (DHF). Echocardiograms and treadmill testing were performed in patients with DHF (n=20) and age-matched hypertension with LV hypertrophy (HTN; n=20). The Minnesota Living with Heart Failure Questionnaire was used to estimate quality of life (QOL). There were no differences in resting blood pressure or echocardiographic parameters between the groups. The maximum exercise time was significantly shorter in the DHF group than in the HTN group (6.0+/-3.0 vs. 12.5+/-2.5 min), and the peak systolic blood pressure during exercise was significantly higher in the DHF group (212+/-18 vs. 189+/-16 mmHg, p<0.05). After 4 weeks of treatment with candesartan, an angiotensin II receptor blocker (8 mg/d), peak systolic blood pressure during exercise decreased to 191+/-13 mmHg, maximum exercise time increased (10.4+/-3.0 min; p<0.05), and QOL improved in patients with DHF, while there was no change in patients with HTN, despite the similar resting blood pressure. In patients with DHF, systolic blood pressure markedly increased during exercise, and this was accompanied by impaired exercise tolerance and a decreased QOL, both of which were partly suppressed by blocking angiotensin II.