Placental blood was harvested using a novel collection system into packs containing citrate-phosphate-dextrose-adenine and then stored for 28 d. Before and during storage, sterility, adequacy of anticoagulation, blood chemistry, and red cell viability were assessed weekly. The average volume of blood collected was 65 mL (range 30-110 mL) with a 0.42 hematocrit once diluted in anticoagulant. All blood culture specimens were sterile at collection and during storage. Adequate anticoagulation (activated partial thromboplastin time > 90 s) on the day of collection was achieved in 15 specimens, all less than 65 mL of blood volume. Ten specimens, in blood volumes ranging from 65 to 110 mL, had mean activated partial thromboplastin time values of 65.3 +/- 10.2 s. Activated partial thromboplastin time values for all 25 specimens at 1, 2, 3, and 4 wk storage were > 90 s, presumably because of the decline in labile clotting factors after 24 h of storage. Hematocrit, red cell ATP, and red cell shape were maintained during storage. As expected, red cell 2,3-diphosphoglycerate declined and potassium levels rose significantly but were not different than levels reported for adult cells similarly preserved. Based on our results, it appears that placental blood represents a potential source of autologous transfusion for the sick neonate over the first month of life.