Background Atrial fibrillation (AF) is a common arrhythmia in heart failure (HF). Plasma concentrations of para-thyroid hormone (PTH) have been shown to increase in HF. The relationship between PTH concentrations and the presence of AF in HF is, however, unknown. This study analyzed the relationship between plasma PHT concentrations and AF in patients with systolic HF.Material and methods 131 consecutive, stable HF patients, who were admitted to the HF outpatient clinic, were included in this prospective, observational study. Patients were classified as those with AF (n = 36) and those in sinus rhythm (SR, n = 95).Results PTH concentrations were markedly higher in patients with AF compared to the patients in SR [85 (15-320) vs. 112 (30-326) U / ml, p=0.007]. PTH, creatinine clearance, hemoglobin, creatinine, age, and left ventricular ejection fraction were found to be related to AF by univariate analysis; though, multivariate logistic regression analysis showed that only PTH concentration was independently related to AF.Conclusion PTH concentrations can be used to indicate AF in patients with systolic HF.