Numerous problems can occur with liquid oxygen delivery systems, in part because of the complexities of such systems. These systems must comply with guidelines of the Joint Commission on Accreditation of Hospitals. During the past year, 18 major problems with the liquid oxygen delivery system have occurred at the authors' hospital. Five times, false alarms have resulted from calibration drift in line pressure sensors. Thrice, excessive depletion of the reverse supply has occurred because of pressure imbalance between the main and reserve systems. Twice, excessive depletion of the reserve supply occurred owing to failure of the vacuum seal on the reserve supply vessel. Eight other potentially serious mishaps have also been reported. These problems, which are inherent in liquid oxygen delivery systems, are for the most part preventable.