AIMS: To investigate whether NT-proBNP before ablation treatment and after exercise testing has predictive information regarding the clinical outcome following pulmonary vein isolation in patients with atrial fibrillation (AF). METHODS: NT-proBNP analysis were obtained before the ablation (before and after exercise test), and repeated at 1, 3, and 12 months after the final procedure. RESULTS: A total of 51 patients were included. At study entry, the median NT-proBNP concentration was 14.0 pmol/L (quartiles: 8.0 and 27.0). After the exercise test, the mean NT-proBNP value increased from 13.0 pmol/L (quartiles: 7.5 and 26.0) to 15.0 pmol/L (quartiles: 9.0 and 34.0), p < 0.001. Following a maximum of two ablations, 22 patients were free of AF while 29 patients experienced recurrent AF. In patients with successful ablation, the mean NT-proBNP concentration at baseline was 10.0 pmol/L (quartiles: 7.0 and 22.2) compared to 22.0 pmol/L (quartiles: 12.0 and 34.5) in patients with ablation failure, p = 0.02. With respect to exercise testing, a trend towards a higher increases during exercise were seen in patients with recurrent AF compared to patients without: 2.0 pmol/L (quartiles 1.9 and 7.0) vs. 1.5 pmol/L (quartiles 0 and 3.0), p = 0.07. A baseline NT-proBNP concentration >15.0 pmol/L was found to be an independent predictor of ablation failure. CONCLUSION: A significantly lower NT-proBNP concentration at baseline and a trend towards a diminished increase during exercise was seen in patients successfully ablated for AF compared to patients with recurrent AF. A baseline NT-proBNP concentration