Within the past two years two drugs, mandelic acid and sulfanilamide, have been added to our armamentarium for the treatment of urinary infections. Both represent advances over the therapeutic measures in use before their introduction. The ketogenic diet was a definite therapeutic advance, and it made it possible to clear up infections in patients with urinary stasis that had previously remained immune to treatment. The difficulties of taking the ketogenic diet were such, however, that Rosenheim1introduced another organic acid, mandelic acid, in place of beta-oxybutyric acid. This was another step forward in the treatment of urinary infections. Mandelic acid can be taken by mouth, and it is excreted unchanged in the urine. Beta-oxybutyric acid and mandelic acid act bactericidally in about the same concentration and in the same range ofpH. Both require organic acid concentrationsof from 0.5 to 1.0 and apHof the urine