In this study, the researchers want to find out how patients who have ultrafiltration (removal of excess fluid) 6 times a week and twice-weekly dialysis (removal of excess fluid and waste products) do in terms of their blood pressure and weight. The researchers believe that maintaining patients at their estimated target weight throughout the week using daily ultrafiltration will reduce their blood pressure to levels shown in other similar studies. Such a reduction in blood pressure may reduce the incidence of cerebral vascular disease, peripheral vascular disease, coronary artery disease, and congestive heart failure. The researchers also believe that patients' quality of life will improve while they are undergoing daily ultrafiltration.

Studies show that more frequent dialysis treatments result in fewer symptoms for patients. The patients feel better and avoid the weight gains and symptoms that patients have on three times a week dialysis. In addition, their blood lab results are better controlled, requiring less medication.

Inclusion Criteria:

• Age greater than or equal to 18 years and less than or equal to 80 years
• Stable three treatments per week dialysis schedule for at least three months prior to beginning the study
• Residual renal clearance <1.5ml/min per 35L of urea volume
• Pre-dialysis serum sodium levels of greater than 136 mEq/L

Exclusion Criteria:

• Non-compliance with hemodialysis treatments--defined as missing more than 1 treatment over the 3 month period prior to the study
• Unable to verbally communicate in English or Spanish
• Current requirement for hemodialysis more than three times per week due to medical comorbidity (including fourth session for ultrafiltration)
• Currently on daily or nocturnal hemodialysis, or less than 3 months since discontinued such treatment
• Expected geographic unavailability at dialysis center during any phase of the trial
• Less than 3 months since the patient returned after acute rejection resulting in allograft failure
• Currently in acute care or chronic care hospital
• Pregnancy
• Current involvement in any non-observational trial
• Unable or unwilling to follow the study protocol for any reason (including mental incompetence)
• Unable or unwilling to provide informed consent or sign IRB-approved consent form
• Pace maker, implantable pump, artificial joint
• Amputation of a limb