Perfusion pumps used for extracorporeal circulation during cardiovascular surgery are usually assembled and primed in the morning immediately before use. Because of the time involved in calling in the perfusionists and setting up the pump, the cardiovascular surgeons at Ingham Medical Center requested that one Sarns 7000 modular heart-lung pump (Sarns Inc./3M, Ann Arbor, Mich.) (Fig. 1) be assembled on Friday before the weekend for possible emergency surgeries during the next 48 to 60 hours to save 30 to 45 minutes. Because of the cost of dismantling a system that had not been used for emergency surgery during the weekend, the pump team expressed a desire to use the pump for surgery on Monday. We could find no data regarding the sterility of the equipment after 48 to 60 hours when a literature search was conducted, and no guidelines or recommendations were available.’ An informal telephone survey of four hospitals in Minnesota, Ohio, and Michigan revealed opinions ranging from those which supported assembling a pump immediately before use to those which supported using an assembled pump up to a month later. To evaluate the sterility and safety of a 48 to 72-hour preassembled pump from an infection control perspective, this preliminary study was conducted. The study was conducted in two phases.