We investigated metabolic, blood gas and acid-base balance modifications of erythrocyte concentrates resuspended in PAGGS-sorbitol solution during 6 weeks of storage. Glucose utilization was impaired during the last 2 weeks, while the intraerythrocytic ATP level decreased only 50% from the 1st to the 6th week. The K+ and Hb concentration in the medium showed a progressive increase which was more pronounced during the last 2 weeks. The decrease in pH progressed to reach 6.27 at the 6th week of storage. Intraerythrocytic 2,3-DPG dropped rapidly in the course of the 1st week and the percentage of oxyhemoglobin showed a remarkable increase after the 1st week (90%). Our data suggest that erythrocyte concentrates in PAGGS-sorbitol should be transfused, for optimal efficacy, within 4 weeks.