We performed a prospective, randomized masked trial to determine whether the use of dedicated units of packed red blood cells equipped with seven satellite bags would reduce donor exposures in infants with birth weights < 1500 gm. We also examined the use of unwashed and older red blood cells. Red blood cells given to the study group were used without washing and until their expiration date (35 to 42 days). Changes in blood pH, potassium, ionized calcium, and hemoglobin were determined with each transfusion and compared with data collected from a control group that received washed, younger red blood cells. There was a 64% reduction in donor exposures in the study group. Changes in infants' blood pH and calcium levels with transfusion were the same in the two groups. There was a clinically unimportant difference in potassium levels. A greater rise in hemoglobin values occurred when washed cells were used. There was no correlation between changes in the blood levels measured and the age of unwashed cells infused. We conclude that the use of red blood cells from satellite bag-equipped dedicated units decreases donor exposures, and that the practices of using only younger red blood cells and of saline washing of red blood cells before infusion, are unwarranted.