Patients with advanced chronic kidney disease have an inability to excrete phosphorus normally leading to high serum concentrations of phosphorus. The hyperphosphatemia is even more pronounced in dialysis patients who often require large doses of phosphorus binders to combat the problem. Hemodialysis is able to remove fair amount of the extra phosphorus; however, the removal is often hampered by the fact that the phosphorus is removed only from the extracellular compartment and phosphorus is mainly intracellular. The end result being a high serum phosphorus concentration at the beginning of dialysis, a sharp decline in the value by the end of dialysis and significant rebound of serum phosphorus concentration a few hours after stopping dialysis as phosphorus moves out of the cells. Here, we describe 2 hemodialysis patients with normal predialysis serum phosphorus concentration and preexisting conditions that made them at risk for developing encephalopathy who developed recurrent obtundation toward the end of the dialysis treatments. After confirming critical postdialysis hypophosphatemia, phosphorus was added to the dialysate baths and the episodes of encephalopathy associated with dialysis ceased.