Bacterial contamination has been the most serious obstacle to the preservation of plasma in the liquid state. Several methods have been proposed to minimize the dangers involved in the accidental use of contaminated plasma,1but none previously proposed have proved adequate. We have instituted the use of the sulfonamide group of drugs in stored plasma as bacteriostatic and bactericidal agents. In all of my experimental work and in actual routine clinical usage over a two year period the method has been found to be completely satisfactory regardless of the temperature (4 C.-24 C.) or duration of storage. The quantity of the drug necessary to accomplish the purpose in stored plasma is small, so that there are no noteworthy contraindications to its routine use. The sulfonamide drugs may be used in conjunction with any of the methods of processing plasma now available. However, since the danger of bacterial contamination of