An examination of the technical and historical literature concerning the discovery and development of antibiotics suggests the possible existence of an era of discovery. This era appears to have a well-defined beginning (about 1940) and a well-defined close (about 1960). It is the purpose of this dissertation to examine the various strands of evidence that support the thesis that a definable antibiotic discovery era does indeed exist. An examination of several antibiotics discovered and developed during the period 1940-1960 support the thesis. One antibiotic in particular, vancomycin, discussed in depth is shown to be exemplary of the trends established about 1940 and which ceased to function about 1960. In concluding, a definition for the discovery era is proposed.