This book is a record of a symposium held under the auspices of the U. S. Department of Health, Education and Welfare, Food and Drug Administration, Division of Antibiotics during October 28, 29 and 30, 1953, in Washington, D. C. Dr. Welch is Director of the Federal Division of Antibiotics, Food and Drug Administration. It is a current record of the “antibiotic era” and accomplishments of the past year. In the introduction, Dr. Welch notes the important economic contribution made through the use of antibiotics, not only to man but to domestic animals and livestock as well. Newer antibiotics also have created problems of human sensitivity and the development of strains of micro-organisms which are drug-resistant. Continued research is directed toward their solution as well as developments in newer uses of recently introduced antibiotics.