Interest has been renewed in CPD-adenine as a long-term liquid blood preservative. The question of whether the metabolic product of adenine, 2,8-dioxyadenine was toxic to humans has apparently been resolved by extensive animal and human studies in favor of there being no potential toxicity in the amounts used in blood preservation. Sweden is adopting CPD-adenine (0.25 mM) as its national blood preservative after ten years of clinical experience in trials. They have shown that each additional week of storage time beyond the current three weeks with CPD results in a 50 per cent reduction of wasteage caused by outdating. They are adopting the 35-day time for regular use with 42 days for an emergency reserve supply. However, many units of blood in the U.S. are stored as packed red blood cells and the question has been raised as to whether there is sufficient glucose in the preservative to maintain red blood cell metabolism in the packed cell unit. The present investigation indicates that there is sufficient glucose for 35 days of packed cell storage in CPD-adenine (0.25 mM) but in some units this might be marginal at 42 days of storage.