BACKGROUND: Depressed heart rate variability (HRV) reflects abnormal cardiac autonomic regulation and has been linked with increased cardiovascular risk and sudden cardiac death. High parathyroid hormone (PTH) levels have also been associated with an increased risk of sudden cardiac death in haemodialysis (HD) patients. Our aim was to investigate the association between HRV indices and PTH in HD patients. METHODS: Continuous intradialytic electrocardiograms were repeated in stable HD patients 5 times every 2 weeks. The absolute values of high-frequency (HF) and low-frequency (LF) HRV components were calculated every 5 min and averaged during the first and last hour of each recording (distinguished by subscripts F and L, respectively). Pre-HD PTH, corrected calcium, and phosphate levels were measured before the first recording. RESULTS: Data were analysed for 75 subjects aged 60 +/- 15, 32% females, 37% diabetics. Baseline biochemical parameters were PTH 44 +/- 32 pmol/l, calcium 2.3 +/- 0.2 mmol/l, and phosphate 1.6 +/- 0.4 mmol/l. All HRV indices showed intra-subject stability over the 5 recordings. Diabetics had lower LFL compared to non-diabetics (-5.5 +/- 0.5 vs. -5.2 +/- 0.5 after logarithmic transformation, p = 0.012). In non-diabetics, PTH correlated negatively with LFL and HFL (LFL r = -0.340, p = 0.020, HFL r = -0.325, p = 0.026) and phosphate correlated negatively with LFF (r = -0.427, p = 0.003), HFF (r = -0.442, p = 0.002) and HFL (r = -0.307, p = 0.040). CONCLUSION: High PTH and phosphate are associated with depressed HRV in non-diabetic dialysis patients. Prospective studies are needed to evaluate the role of mineral abnormalities in autonomic imbalance and arrhythmic risk in HD patients.