P50, 2,3-diphosphoglycerate (DPG), inorganic phosphorus (Pi), adenosine triphosphate (ATP), and blood gases were measured daily in 23 patients with burn injuries, until their death or discharge from the ICU. At the time of admission, P50values were high. In nonsurvivors, P50started to decline 1 week after the injury. Corrected P50values to pH 7.4 were well correlated with DPG values. In survivors, P50tended to correlate with Pi values, but in nonsurvivors at the septic or terminal stage, the values of P50did not correlate with Pi or ATP. Low P50predicted the poor outcome of severely burned patients. At the convalescent stage of major burn injury, P50and DPG were higher than normal and often remained elevated for weeks.