BACKGROUND: AS-7 is a new alkaline hypotonic red cell additive solution (AS) shown to improve red cell quality during storage compared with AS-1. We sought to compare red cells stored in AS-7 with those stored in SAGM using RCC that were either untreated, or washed or irradiated on day 14 of storage. STUDY DESIGN AND METHODS: A pooled and split study design was used to produce seven identical RCC (four in SAGM and three in AS-7). At day 14 following donation, two RCC (one in SAGM and one in AS-7) were gamma irradiated and three RCC (two in SAGM and one in AS-7) were washed and resuspended in either SAGM or AS-7. RCC were sampled for analysis throughout storage and at end of shelf life: day 28 for washed or irradiated and day 35 for untreated RCC. RESULTS: For untreated, washed or irradiated RCC, those stored in AS-7 had lower haemolysis, red cell microvesicles and supernatant potassium content than RCC in SAGM. In addition, ATP levels and pH were better maintained in AS-7 RCC than in SAGM RCC. CONCLUSION: These data suggest that the quality of these components may be improved by storage in AS-7 compared with SAGM.