A newborn transfusion cell washing device generally comprising a disposable, graduated test tube shaped container having a cap with an inlet port, an injection/sampling port, a suction port, and a vent. The container is capable of being inserted into a conventional clinical centrifuge. The device requires a relatively small volume to operate, 25 ml or less per procedure, and can be performed easily by any hospital blood bank technologist without any special skills. Washed RBCs can be provided to the patient in a timely manner, without the need for "fresh blood." Any in-dated RBCs can be washed to remove excessive potassium and other toxins. The main RBC aliquot can be saved and repeatedly sampled until the unit is expired or exhausted. This provides a cost savings to the hospital and more importantly, minimizes the recipient's donor exposure.