This review discusses the development of chemotherapy of bacterial infections by aromatic sulfonamide compounds, and summarizes the data on the organisms against which sulfanilamide has been found to be effective. The mechanism of its action is also discussed. The drug is most valuable in infections due to type A organisms of the B-hemolytic streptococci. It has shown its value against meningococcus, gonococcus, E. typhi, E. paratyphi B, Clos-tridium welchii, the Sonne strain of dysentery bacillus, and a staphylococcus. It is found to be of value against certain strains of pneumococcus. The wt. of the evidence is in favor of the view that the substance acts purely as a bacteriostatic agent, although under certain conditions it may be bactericidal. A conc. of 10 mg.% in the blood stream seems to be necessary for full effectiveness. The toxic symptoms and idiosyncrasies that may be met in the clinical use of the drug are also discussed.