Abstract. Plasma adenine concentration was measured in five units of citrate‐phosphate‐dextrose‐adenine (0.25 mmol/1 adenine) whole blood during storage at +4°C. The adenine levels decreased to 50% in 9–10 days and to approximately 15% in 3 weeks. In spite of this rapid consumption of adenine, the adenosine triphosphate levels were well maintained: almost 100% after 3 weeks and 60% after 6 weeks of storage.