We aimed to identify whether N-terminal fragment of pro-brain natriuretic peptide (NT-proBNP) at peak exercise can provide incremental clinical information over resting levels. A total of 90 patients with systolic heart failure were prospectively studied. Levels of plasma NT-proBNP were assessed at rest and at peak exercise during a cardiopulmonary exercise test. Patients were followed-up for 30 ± 10 months. Levels of NT-proBNP at baseline and peak exercise were significantly correlated with left ventricular ejection fraction ([LVEF] r = -.629, P < .001 and r = -.630, P < .001, respectively) and peak oxygen uptake ([Vo (2)] r = -.752, P < .001 and r = -.740, P < .001, respectively). Levels of plasma NT-proBNP at peak exercise demonstrated similar predictive ability for the detection of patients with low peak Vo (2) and LVEF <28%. Levels of plasma NT-proBNP can detect low-functional class patients and patients who may be the candidates for heart transplantation with high sensitivity and specificity. At baseline and peak exercise, NT-proBNP demonstrates similar prognostic and predictive ability.