Background: Older patients with heart failure with preserved ejection fraction have severe exercise intolerance. Vitamin D may play a role in cardiovascular and skeletal muscle function, and may therefore be implicated in exercise intolerance in heart failure with preserved ejection fraction. However, there are few data on vitamin D status and its relationship to exercise capacity in heart failure with preserved ejection fraction patients.Methods: Plasma 25-hydroxyvitamin D (25[OH]D) and exercise capacity (peak oxygen consumption, [VO2], 6-minute walk distance) were measured in 112 older heart failure with preserved ejection fraction patients (mean ± SD age = 70 ± 8 years) and 37 healthy age-matched controls.