Prior to the 1970s, microorganisms were primarily identified with conven­ tional biochemical tests and often required several days to weeks for identi­ fication. In the early 1970s, API (bioMerieux Vitek) introduced lyophilized substrates in microcupules that allowed many clinical isolates to be identi­ fied in 24-48 hr. Subsequently, with use of a heavy inoculum, preformed enzymes could be detected, allowing some bacteria to be identified in 4 hr. In the latter half of the 1970s, automated identification systems were intro­ duced. Our discussion will be limited to identification systems that have automated result entry, have a data base for the identification of a large variety of different microorganisms and are available in the United States.