A new approach to the treatment of boric acid poisoning is presented. In the absence of any antidote or specific therapy for this type of poisoning, an exchange transfusion using a quantity of blood approximately 4 times the patient's blood volume was performed. The amount of boric acid removed was quantitatively measured by a technique which is described. The values thus obtained demonstrated that the exchange transfusion resulted in the removal of at least 36 per cent of the total boric acid in this infant's body. Twenty-four hours later a second exchange transfusion was performed using a volume of blood 2 times the infant's circulating blood volume. This exchange was shown to have resulted in the removal of 20 per cent of the remaining boric acid. In view of the high mortality rate previously reported in similar cases, we believe that the performance of this procedure on our patient materially contributed to his recovery. The favorable evidence presented in this report, suggests that exchange transfusion should be undertaken in selected cases of boric acid poisoning and is worthy of further evaluation. Semi-quantitative and quantitative techniques for the estimation of the boric acid content of blood and urine are described.