Dihydroxyacetone (DHA) is effective in maintaining 2,3-diphosphoglycerate (2,3-DPG) concentrations in stored red blood cells. One limitation to the use of DHA is its instability when added to anticoagulant solutions during blood bag manufacture. The stability of DHA solutions have been evaluated. Solutions of DHA are stable at 25 C in water or isotonic saline, with or without the addition of glucose or adenine. DHA is stable to autoclaving; 99 + per cent surviving at 150 mM, and 89 per cent surviving at 1.9 M concentrations. DHA can be incorporated into a satellite addition pouch attached to the main blood drawing bag, and be added to the blood-anticoagulant mixture after phlebotomy or the preparation of red blood cells. Addition of the DHA solution, containing adenine and extra glucose, to packed cells causes significantly improved maintenance of 2,3-DPG during 42 days of 4 C storage, while maintaining adequate concentrations of red blood cell ATP. The use of DHA, adenine, and glucose in extended storage of packed cells, using either zero or seven day addition of the nutrient solution, produces similar efficacious results.