This chapter provides an overview of green metrics and their historical role in promoting the development of green chemistry. Starting with the history of the field, the Twelve Principles of Green Chemistry are introduced and discussed in conjunction with a "green-by-design" approach recently applied to the synthesis of Lipitor ® . Various perspectives on synthetic efficiency are briefly outlined with reference to atom economy and E factor. These ideas are further explored in the context of three industrial processes which have received Presidential Green Chemistry Challenge Awards. The synthesis of ibuprofen is examined from the point of view of intrinsic efficiency. Using the BHC process as an example, several benefits associated with the use of catalysis are discussed, with an emphasis placed on designing atom-efficient reactions. A global perspective centered around the production of chemical waste is also outlined with reference to Merck's commercial synthesis of Januvia ® , a medication for the treatment of type II diabetes. Finally, Pfizer's new sertraline process is used to describe ways of improving both quantitative as well as qualitative aspects of an industrial synthesis. The chapter concludes with a brief outline of the future directions of green metrics.