['To evaluate the best combination of clinical parameters and brain natriuretic peptide (BNP) or N-terminal pro-BNP (NT-proBNP), to predict diastolic dysfunction (DD) in heart failure with preserved left ventricular ejection fraction (HF-PLEF) as determined by Doppler-echocardiography.', 'HF patients with EF >40% in the CHARM Echocardiographic Substudy were included and classified to have normal diastolic function, or mild, moderate or severe diastolic dysfunction. Plasma BNP and NT-proBNP levels were measured and relevant clinical characteristics recorded. 181 participants were included in this analysis, 72 (40%) had moderate to severe DD. A model including age, sex, BNP, body mass index, history of atrial fibrillation, coronary artery disease, diabetes mellitus, hypertension and left atrial volume was highly predictive of moderate to severe DD; AUC 0.81 (0.73-0.88; p<0.0001). Similarly, substitution of BNP with NT-proBNP resulted in an AUC 0.79 (0.72-0.87; p<0.0001). In these models; BNP>100 pg/ml (OR 6.24 CI 2.42-16.09, p=0.0002), history of diabetes (OR 3.52 CI 1.43-8.70, p=0.006) and NT-proBNP >600 pg/ml (OR 5.93 CI 2.21-15.92, p=0.0004), history of diabetes mellitus (OR 2.75 CI 1.12-6.76, p=0.03) respectively remained independent predictors of DD in HF-PLEF.'] Do bNP and NT-proBNP predict echocardiographic severity of diastolic dysfunction?