The in vitro activities of tigecycline against 1,924 clinical isolates were examined. The new glycylcycline exhibited excellent activity against all gram-positive cocci (MICs at which 90% of the isolates tested were inhibited [MIC(90)s], <or=1 microg/ml). In addition, it was also very potent against most members of the Enterobacteriaceae, with most MIC(90)s being <or=2 microg/ml. Among the nonfermenters, Acinetobacter spp. and Stenotrophomonas maltophilia are included in the in vitro spectrum of tigecycline activity.