Blood-compatible, chlorine-free polymers such as a flexible, non-toxic, sterilizable polyester plastic formulation may contain from 5 to 70 percent by weight of a blood-extractable plasticizer such as di-2-ethylhexylphthalate, to cause blood which is stored in contact with the polymer to exhibit a surprisingly low hemolysis rate when compared with corresponding polymers which are free of the plasticizer. Accordingly, blood bags, tubing and other medical blood-contacting devices may be advantageously made from these polymers.