Previous studies with CPDA-1 and Nutricel preserving solutions indicated that red cell properties were affected by small differences in storage temperature. The influence of a 3°C differential on the preservation of the in vitro properties of ADSOL-preserved (AS-1) red blood cells was investigated in a paired study. AS-f red blood cells were stored at 2.5 and 5.5 °C for 42 days. Extent of hemolysis, glucose consumption and pH levels were comparable at the two storage temperatures. Lactate levels were slightly, but significantly higher at 5.5°C. ATP levels were slightly but significantly higher at 2.5°C, only during the later part of the storage period. 2.3-DPG levels were slightly better retained at 2.5 °C after 7 days of storage. Holding units of whole blood for either 1 or 8h at ambient temperature after phlebotomy prior to processing did not influence the types of temperature-dependent changes. The differences as a function of storage temperature were small and appear to be of no practical importance in connection with the storage of AS-1 red blood cells.