Studies were conducted on a method of direct inoculation of MicroScan overnight and rapid panels from positive BacT/Alert blood culture bottles containing standard aerobic media to determine the correlation with inoculation of the corresponding panels with a standardized bacterial suspension obtained following subculture to agar. For Gram-negative organisms, 122 of 127 (96%) overnight panels and 85 of 118 (72%) rapid panels showed complete agreement with the standard method for species identification. Highest concordance (99%) occurred with Enterobacteriaceae inoculated directly into overnight panels. For Gram-positive organisms, 70 of 85 (82%) overnight panels and 45 of 86 (52%) rapid panels showed complete agreement. These findings suggest that direct inoculation of Gram-negative overnight MicroScan panels yields results most comparable to standard methods when Enterobacteriaceae are detected and allows reporting of results 18 to 24 h sooner. Direct inoculation of Gram-positive overnight or rapid panels and Gram-negative rapid panels from this blood culture medium did not yield acceptable identification results and is not recommended. Copyright (C) 1998 Elsevier Science Inc.