Background: We proposed a new method to estimate dry weight (DW) using single frequency bioimpedance. Methods: We hypothesized that the change in whole body resistance at 50 kHz (R50) was proportional to the ultrafiltration volume (UFV) during a hemodialysis (HD) session. When the targeted resistance estimated in healthy subjects was reached, the patient achieved his/her DW. UFV and R50 were monitored in 40 HD patients. Another 43 HD patients were stratified into 2 groups to validate this method. Results: The change in whole body resistance was proportional to UFV in each of the 40 HD patients. In the DWdecrease group, pre-dialysis systolic blood pressure (n = 29, 154.5 ± 22.8 vs. 146.9 ± 22.3, p < 0.05) and antihypertensive medicine (4.7 ± 3.6 vs. 3.3 ± 2.2, p < 0.05) decreased without adverse symptoms change. In the DWincrease group, the number of adverse symptoms in 1 week (n = 14, 26 vs. 6, p < 0.05) decreased without a change in systolic blood pressure. Conclusion: This method may become a convenient and cheaper way to estimate DW in HD patients.