On 15 newborn infants, 31 exchange transfusions were performed, 11 with previously frozen red blood cells resuspended in albumin-electrolyteglucose solution, 4 with previously frozen red blood cells resuspended in fresh frozen plasma and 16 with ACD blood. Good clinical effects were obtained in all cases and no untoward clinical reactions were noticed. More pronounced decreases in vB pH and vB standard bicarbonate were noted after exchange transfusions with frozen blood than after ACD blood transfusions. Small and unimportant changes of plasma electrolytes were recorded following exchange transfusions with frozen blood. The P-haemoglobin concentrations were higher in the frozen blood than in the ACD blood, resulting in an increase of P-haemoglobin following exchange transfusion with frozen blood. The wash-out effect of the frozen blood was indicated by a reduction of platelets, fibrinogen and IgG during the exchange transfusions to 20% of the original value. Furthermore, a decrease in coagulation capacity was observed as revealed by considerable changes in TT and APTT values. For newborn infants with suspected or manifest coagulation disorders and for newborn infants needing more than one exchange transfusion, frozen, thawed and washed red blood cells should be resuspended in fresh or fresh frozen plasma when used as transfusion blood.