Sulfathiazole, a derivative of sulfanilamide, was submitted to us for clinical investigation. Laboratory and animal experimental work indicated a low degree of toxicity and a high degree of protection against many virulent organisms, especially the staphylococcus, pneumococcus and gonococcus. This study includes 200 controlled patients. The drug was administered orally in 0.5 Gm. tablets to adults, smaller portions being given to children and babies. The sodium salt was given intravenously, a 1 Gm. ampule dissolved in 100 cc. of sterile distilled water injected slowly. The powder was used locally, sprinkled generously in infected wounds or introduced by insufflation into cavities. A study of the absorption, dosage, toxicity and effectiveness of the drug follows: ABSORPTION The absorption of the thiazole compounds when given by mouth is quite variable, much more so than that of sulfanilamide or sulfapyridine. For example, one patient receiving 6 Gm. daily had a concentration in the blood