SummaryThein vitroactivity of cefroxadine was studied and found to he at least comparable to that previously reported for cefalexin and cefradine. The activity of cefroxadine was superior to that of amoxicillin against tested isolates.Time-killing studies showed that the addition of 4×minimum inhibitory concentration (MIC) of cefroxadine to growing cultures reduced viable counts by 4 log units within a 3 h incubation. A diffusion test with a 30μg cefroxadine disk produced acceptable interpretive results with tentative zone size breakpoints of≤14 mm for resistance and≥17 mm for susceptibility.