Abstract Background: Brain Natriuretic Peptide (BNP) levels increase in response to exercise in congestive heart failure patients. However, the timing, degree, and clinical consequences of exercise-related BNP elevation in Pulmonary Arterial Hypertension (PAH) remain unexplored. Materials and methods: A total of 38 consecutive PAH patients were enrolled in this study. BNP levels were drawn prior to, and 6, 14, 20, and 60 minutes following, the six-minute walk test. Subjects were divided based on BNP level cut off used in our laboratory: BNP ≤100pg/ml and BNP >100pg/ml. Time to Clinical Worsening (TTCW) was defined as a composite end point of death, transplant, prostacyclin initiation, or hospitalization for worsening PAH. Results: Twenty-four patients were in the BNP ≤100pg/ml group (44±28pg/ml, mean ± SD) and fourteen patients in the BNP >100pg/ml group (285±179pg/ml). Baseline six-minute walk distance in the ≤100pg/ml group was higher as compar...