Objective: Circulating levels of brain-derived neurotrophic factor (BDNF) is reduced in patients with major depression and type-2 diabetes. Since acute exercise increases BDNF production in the hippocampus and cerebral cortex, we hypothesized that endurance training would enhance the release of BDNF from the human brain as detected from arterial and internal jugular venous blood samples. Methods: In a randomized controlled study, twelve healthy sedentary males performed three months of endurance training (n = 7) or served as controls (n = 5). Before and after the intervention, blood samples were obtained at rest and during exercise. Results: At baseline, the training group (58 ± 106 ng 100 g-1 min-1, mean ± SD) and the control group (12 ± 17 ng 100 g-1 min-1) had a similar resting release of BDNF from the brain. Three months of endurance training enhanced the resting release of BDNF to 206 ± 108 ng 100g-1 min-1 (P < 0.05), with no significant change in the control subjects, but there was no training-induced increase in the release of BDNF during exercise. Additionally, eight mice completed a 5-week treadmill running training protocol that increased the BDNF mRNA expression in the hippocampus (4.5 ± 1.6 vs. 1.4 ± 1.1 mRNA/ssDNA; P < 0.05), but not in the cerebral cortex (4.0 ± 1.4 vs. 4.6 ± 1.4 mRNA/ssDNA) as compared to untrained mice. Conclusion: The increased BDNF expression in the hippocampus and the enhanced release of BDNF from the human brain following training suggests that endurance training promotes brain health.