The increasing use of para-aminobenzenesulfonamide in the treatment of streptococcic infections has prompted us to report the results which we have obtained on the absorption and excretion of this drug. Although these results offer by no means a complete and finished study of the subject, the obvious application of certain of our observations to the therapeutic use of the drug and the simple method that has been devised for determining the substance in blood and urine would appear to justify a presentation of our preliminary results at this time. METHOD OF ANALYSIS The method for analysis of blood and urine (as well as certain other body fluids) is based on diazotization of the aminobenzenesulfonamide with nitrous acid, and coupling the resulting diazo compound in acid solution with dimethyl-a-naphthylamine to produce a purplish red azo dye which can easily be estimated by colorimetric comparison. This reaction depends on the presence of