The experimental basis for the use of succinylsulfathiazole as an agent for altering the flora of the gastrointestinal tract is presented in other papers by us.1 In those communications the contents of the gastrointestinal tract were described as being profoundly altered by the oral administration of succinylsulfathiazole to experimental animals and man. Such a modification of the intestinal flora suggests the use of this drug especially in the preoperative preparation of the large bowel. Succinylsulfathiazole has been given to 100 human beings without severe untoward reactions which could definitely be ascribed to its administration. The 100 patients receiving succinylsulfathiazole may be grouped as indicated in table 1. The knowledge gained from an intensive study of the cases of these patients as it pertains to surgical procedures is the basis for this communication. LOCAL BACTERIOSTATIC ACTION OF SUCCINYLSULFATHIAZOLE Succinylsulfathiazole is so poorly absorbed from the gastrointestinal tract that only an