Enterobacteriaceae Biochemical Cards (EBC) may be used in the AutoMicrobic system for identification of enteric bacilli. Recently, the card has been modified to permit identification of enteric and certain nonenteric bacilli. Also, minor modifications have been in the computer program used for interpretation of tests with the new cards (EBC+). The two types of cards (EBC and EBC+) were tested in parallel and found to be in agreement with 97% of 650 Enterobacteriaceae. Most of the discrepancies were resolved when selected strains were retested on 3 separate days. A lack of absolute reproducibility with either system was demonstrated and explained most of the initial discrepancies. Approximately 97% of the AutoMicrobic system identifications agreed with those obtained from standard reference methods, after equivocal AutoMicrobic system results (P less than 0.80) were excluded. Equivocal responses occurred with 4% of our EBC tests and 7% of our EBC+ tests; additional tests are needed before such strains can be identified with confidence.