Data are presented for percentage of recovery, survival time (T1/2) and mode of sequestration of erythrocytes from ACD [disodium citrate 95 mmol/l and glucose (C6H12O6 X H2O)] 152 mmol/l or ACD--adenine or adenine + guanosine (pH ranging from 5.0 to 5.6) preserved blood for 35 days at 4-8 degrees C (277-281 K). With the availability of guanosine in 0.25 mmol/l or 0.5 mmol/l final concentration in ACD + 0.25 or 0.5 mmol/l adenine preserved blood a positive effect can be exerted on erythrocyte 24 hrs recovery and survival time (T1/2). This effect is particularly evident when pH of the preservative solution is raised to 5.6. Final concentrations of 0.25 mmol/l adenine and guanosine in ACD preserved blood (whole or packed erythrocytes, pH 5.6, Hct. 0.73 or 0.61) are sufficient to ensure 35 days of storage at 4-8 degrees C (277-281 K).