The activities of tigecycline and comparators against isolates collected from 76 U.S. centers between January 2004 and September 2005 were assessed. Tigecycline MIC90S were ≤2 μg/ml for Klebsiella pneumoniae, Klebsiella oxytoca, Escherichia coli, Enterobacter aerogenes, Enterobacter cloacae, Serratia marcescens, Acinetobacter baumannii, Staphylococcus aureus, Enterococcus faecalis, Enterococcus faecium, and Streptococcus agalactiae. Copyright © 2006, American Society for Microbiology. All Rights Reserved.