Sanfetrinem, formerly GV104326, is a new trinem antimicrobial agent with extensive in vitro activity for a variety of different bacteria. The activity of sanfetrinem was determined using a broth microdilution MIC method versus a large number of clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis obtained in a recent 30-center United States surveillance study. The sanfetrinem MIC50 and MIC90 values for these three organism groups were 0.015 and 0.5 microgram/ml, 0.25, and 0.5 microgram/ml, and 0.015 and 0.03, respectively.