Human red blood cells preserved with approximately 45 per cent w/v glycerol, frozen by the slow freeze‐thaw technic, and stored at ‐80 C for up to six years were evaluated by measurements of the posttransfusion survival of autologous51chromium‐labeled red blood cells, the per cent recovery of the preserved red blood cells, supernatant hemoglobin in the unit, and intracellular potassium levels. The glycerolized red blood cells were washed either with electrolyte solutions using continuous centrifugation, or by dilution with nonelectrolyte solutions and recovery of the red blood cells by agglomeration (Huggins technic). Glycerolized red blood cells stored frozen for more than two years and washed by the Huggins technic had significantly decreased postthaw stability when the de‐glycerolized red blood cells were kept after thawing for longer than four hours at 4 C. Glycerolized red blood cells stored frozen for up to six years and washed by continuous centrifugation with electrolyte solutions showed clinically acceptable post‐transfusion survival after postthaw storage at 4 C for up to 24 hours. The results of washing glycerolized red blood cells by continuous centrifugation showed that prior dilution of the thawed cells with a ten per cent glycerol solution was vitally important. The method used in washing glycerolized red blood cells may significantly limit the length of time that red blood cells may be stored at 4 C after having be