Two patients with renal failure presented postoperatively with marked hyperphosphatemia and symptomatic hypocalcemia. This phosphate intoxication was due to a commonly used phosphate-containing enema. An increase in phosphatemia was also seen in two other patients prospectively followed after receiving the same product. The phosphate increase depends upon the retention duration of the enema. The use of phosphate-containing enemas in patients with renal failure is not entirely risk-free.