Patients with diastolic heart failure (HF), i.e., clinical HF with normal or near normal left ventricular ejection fraction (LVEF), may develop unstable angina pectoris (UAP) due to epicardial atherosclerotic coronary artery disease and/or to subendocardial ischemia, even in the absence of coronary artery disease. However, the risk of UAP in ambulatory patients with diastolic HF has not been well studied. We examined incident hospitalizations due to UAP in 916 patients with diastolic HF (LVEF >45%) without significant valvular heart disease and 6,800 patients with systolic HF (LVEF <or=45%) in the Digitalis Investigation Group trial. During a 38-month median follow-up, 12% of patients (797 of 6,800) with systolic HF (incidence rate 435 per 10,000 person-years) and 15% of patients (138 of 916) with diastolic HF (incidence rate 536 per 10,000 person-years) were hospitalized for UAP (adjusted hazard ratio for diastolic HF 1.22, 95% confidence interval [CI] 1.02 to 1.47, p = 0.032). There was a graded increase in incident hospital admissions for UAP with increasing LVEF. Hospitalizations for UAP occurred in 11% (520 of 4,808, incidence rate 407 per 10,000 person-years), 14% (355 of 2,556, incidence rate 496 per 10,000 person-years), and 17% (60 of 352, incidence rate 613 per 10,000 person-years) of patients with HF, respectively, with LVEF values <35%, 35% to 55%, and >55%. Compared with patients with HF and an LVEF <35%, the adjusted hazard ratios for UAP hospitalization in those with LVEF values 35% to 55% and >55% were, respectively, 1.17 (95% CI 1.02 to 1.34, p = 0.028) and 1.57 (95% CI 1.20 to 2.07, p = 0.026). In conclusion, in ambulatory patients with chronic HF, a higher LVEF was associated with increased risk of hospitalizations due to UAP. As in patients with systolic HF, those with diastolic HF should be routinely evaluated for myocardial ischemia and managed accordingly.