BACKGROUND: Hypertension is a common problem for hemodialysis patients and is associated with an increased cardiovascular mortality. We analyzed ambulatory blood pressure (ABP) in hemodialysis patients and investigated if an adjustment of dry weight can be used to control blood pressure. METHODS: ABP was measured for twenty-four hours after hemodialysis. A bioimpedance Analysis (BIA) was conducted. Patients were divided into two groups by the edema index. A normohydration (NH) group included patients with the edema index less than 0.40, and an overhydration (OH) group included patients with the edema index 0.40 or more. We accordingly adjusted the dry weight based on BIA results. RESULTS: Thirty-six patients were recruited, comprising twenty-two men and fourteen women. In regard to the ABP, 24-hour systolic and diastolic blood pressures were 140.2 +/- 19.7 mm Hg and 79.0 +/- 10.6 mm Hg, respectively. There was a significant association between 24-hour systolic blood pressure and the edema index (r = 0.501, p = 0.002). Twenty four-hour systolic blood pressure was significantly different between the NH and OH groups (median value, 132.0 vs. 150.5 mm Hg; p = 0.008). In OH group, after adjustment of the dry weight, the edema index was decreased from 0.411 +/- 0.009 to 0.389 +/- 0.047 and office systolic blood pressure was also decreased from 144.7 +/- 32.7 mm Hg to 125.3 +/- 15.4 mm Hg in OH group (p = 0.028 and p = 0.018, respectively). CONCLUSIONS: The edema index obtained by the bioimpedance analysis is significantly correlated with 24-hour systolic blood pressure in hemodialysis patients. Also, an adjustment of dry weight can be used to control blood pressure in hemodialysis patients.