Unpublished data made available to us1suggested that the new antibiotic, aureomycin, was of low toxicity, was effective in vitro against a large variety of gram-positive and gram-negative bacteria and was particularly effective in experimental infections with rickettsias and with viruses of the psittacosis-lymphogranuloma venereum group. Clinical trials to determine its field of usefulness, therefore, seemed warranted. The results of the oral use of this antibiotic in 100 cases of a variety of bacterial infections are of sufficient interest to warrant this report. A brief résumé of the results of laboratory studies carried out in the course of this clinical study is also included. Further details will be presented in separate communications. BACTERIOLOGIC STUDIES Sensitivity of Bacteria.— Tests for sensitivity to aureomycin were carried out by tube dilution or streak plate methods on one hundred and eighty-six strains of pathogenic bacteria recently isolated from patients at the Boston City