We report a 76-year-old man, stable on a thrice-weekly hemodialysis program over a period of 3 years, who developed acute intradialysis hemolysis secondary to hypophosphatemia, an unusual cause of hemolysis. During the dialysis session we monitored the starting point, the severity and duration of intradialysis hemolysis. Severe hyphosphatemia is a rare cause of intradialysis hemolysis. It is important to think of his possibility to make an adequate diagnosis and treatment. The patient was treated with a phosphorus-enriched acid concentrate, bicarbonate-buffered dialysate, with biochemical and clinical improvement.