['Brain-derived neurotropic factor (BDNF) is involved in cardiovascular diseases as well as skeletal muscle energy metabolism and depression. We investigated whether serum BDNF level was associated with prognosis in patients with heart failure (HF).', 'We measured the serum BDNF level in 58 patients with HF (59.2 ± 13.7 years old, New York Heart Association functional class I-III) at baseline, and adverse events, including all cardiac deaths and HF rehospitalizations, were recorded during the median follow-up of 20.3 months. In a univariate analysis, serum BDNF levels were significantly associated with peak oxygen capacity (β\xa0= 0.547; P\xa0= .003), anaerobic threshold (β\xa0= 0.929; P\xa0= .004), and log minute ventilation/carbon dioxide production slope (β\xa0= -10.15; P\xa0= .005), but not Patient Health Questionnaire scores (β\xa0= -0.099; P\xa0= .586). A multivariate analysis demonstrated that serum BDNF level was an independent prognostic factor of adverse events (hazard ratio 0.41, 95% confidence interval 0.20-0.84; P\xa0= .003). The receiver operating characteristic curve demonstrated that low levels of BDNF (<17.4 ng/mL) were associated with higher rates of adverse events compared with high levels of BDNF (≥17.4 ng/mL; log rank test: P < .001).'] Does serum brain-derived neurotropic factor level predict adverse clinical outcomes in patients with heart failure?