Objective: One of the major causes of death in end-stage renal disease (ESRD) patients under maintenance hemodialysis (HD) is ventricular arrhythmias (VA). Heart rate variability (HRV) has been claimed to be related to disturbance of autonomic nervous system and therefore a predictor for VA occurrence. The purpose of this study is to evaluate the relationship between the HRV parameters and electrolytes before and after hemodialysis in ESRD patients. Methods: There were 23 ESRD patients recruited for the study. Electrolytes for the analysis are Ca+2, P+3, Na+, K+, Cl-. Single lead electrocardiographic signal was recorded for five minutes and the HRV parameters (time-domain) were then derived by a Taiwanese CheckMyHeart machine. Time-domain parameters used were SDNN, RMSSD, NN50. SAS version 8.2 was used for the statistical analysis and paired student t test was adapted to evaluate the statistical significance of their changes. Pearson’s partial correlation coefficients were also derived from the same software. Results: All electrolytes except chloride changes before and after hemodialysis were shown to be statistically significant analyzed by paired Student’s test. Body weight changes significantly reduced from 57.57±6.78 kg to 55.26±9.92 kg (p<0.001) after the hemodialysis. Time-domain HRV parameters were shown to increase significantly after hemodialysis. There was no correlation between electrolytes changes and time- domain and frequency-domain HRV parameters after hemodialysis. Conclusions: 1. All electrolyte changes before and after HD were statistically significant. 2. HRV parameters (SDNN, NN50 and rMSSD) significantly increased after HD. 3. QTc and QT intervals decreased after HD. 4. Partial correlation analysis revealed that there was no statistically significant correlation between electrolytes changes and the HRV parameters.