Patients with diastolic heart failure (DHF) show symptoms of classical heart failure but have normal left ventricular systolic function. Exercise intolerance in DHF patients should be evaluated objectively by measurements with proven prognostic value such as peak oxygen consumption (VO 2peak), ventilatory threshold (VT), and the ratio between minute ventilation and carbon dioxide production (VE/VCO 2 slope). The six-minute walk test shows wide variability and only a modest correlation with VO 2peak. Thus, this test is unacceptable when accurate values are needed for risk stratification. Like patients with systolic heart failure, patients with DHF have markedly reduced values of VO 2peak and VT, and elevated VE/VCO 2 slope. DHF patients have shown an improvement in exercise tolerance, measured by VO 2peak and VT, following training, suggesting that exercise therapy that has been successful for systolic heart failure may have a role in DHF therapy.