A total of 1834 non-copy, general practice or outpatient isolates were collected by 20 hospital laboratories within the British Isles, and identified and tested for susceptibility to nine antimicrobial agents available by oral administration at one centre. Against Enterobacteriaceae cefpodoxime was the most active β-lactam agent tested, the MIC90s being: For Escherichia coli 1.0 mg/1, for Proteus mirabilis 1.0 mg/l, for Citrobacter spp. 2.0 mg/l, and for Enterobacter spp., Serralia spp., Morganella spp. and Klebsiella spp. 16–64 mg/l. Cefpodoxime also showed a certain amount of activity against staphylococci and high activity against streptococci, the MIC90s being for Staphylococcus aureus 2 mg/1, for coagulase negative staphylococci 8 mg/1, for Streptococcus pyogenes 0.015 mg/l, for Str. pneumoniae 0.06 mg/1 and for Str. agalactiae 0.5 mg/1. © 1990 The British Society for Antimicrobial Chemotherapy.