The discovery that certain derivatives of sulfanilamide are relatively poorly absorbed from the gastrointestinal tract marked the beginning of a new era in intestinal antisepsis. One of these compounds, sulfaguanidine, has been given extensive clinical trial and has been found to be of value in the treatment of patients with acute bacillary dysentery 1 and of dysentery carriers. 2 In cases of typhoid, 3 the typhoid carrier state 4 and ulcerative colitis, 3 the results have been discouraging. Patients undergoing extensive operations on the bowel were also given this drug with the hope that reduction of the number of gram-negative bacilli in the intestinal contents might cause a decrease in the incidence of infections of the peritoneal cavity due to fecal contamination. It was not entirely satisfactory for this purpose, partly because it was absorbed into the blood stream to such an extent that it gave rise to frequent and