SummaryFrom the small series of animals receiving oral bacitracin, the following significant facts were obtained: 1. Fecal streptococci and spore forming anaerobes were greatly reduced in the intestine at a dosage between 2,000 and 10,000 u/kg per day. 2. Coliform organisms were little affected by bacitracin. 3. Bacitracin persisted in the feces as long as 3 days following cessation of treatment. 4. Bacitracin was absorbed from the intestinal tract as evidenced by significant blood levels. 10,000 u/kg per day was sufficient to produce blood levels as high as 0.085 u/cc of plasma 1 hour after administration. 5. Additional evidence of absorption was obtained by the finding of high levels of bacitracin in the urine. The highest obtained with 10,000 u was 0.22 u/cc and with 20,000 u 1.65 u/cc of urine.