There are numerous approaches to the identification of the Enterobacteriaceae in the clinical laboratory. Accuracy in identifying organisms is related directly to the skill and experience of the user and to the number of tests inoculated. Many of the commercially available kits offer reproducibility, convenience, accuracy, and ease of storage, particularly for smaller hospital laboratories that have neither the facilities nor the expertise to prepare and exert quality control over microbiologic media. However, none of the kits offers the accuracy and few offer the flexibility available through the use of conventional media, the variety and duration of incubation of which are virtually unlimited. The proper use of any system requires training because accurate identification requires the concurrent examination of colonial morphology and biochemical reactions-manufacturer's flow charts, reaction tables, or printed recognition systems notwithstanding. Microbiologists should be wary of new systems before impartial evaluations have been performed and published in scientific journals; manufacturers' technical literature and salesmen's presentations are, for obvious reasons, seldom objective.