We studied the in vitro activity of gemifloxacin (SB-265805) and 14 comparator antimicrobials against 288 recent isolates of enteropathogenic bacteria (106 Salmonella: spp., 32 Hafnia alvei, 22 Yersinia enterocolitica, 21 Shigella: spp., 16 Aeromonas: spp. and 91 Campylobacter jejuni). Gemifloxacin, the other fluoroquinolones and cefotaxime were very active against all microorganisms tested except for C. jejuni. Seventy-seven per cent of isolates of C. jejuni were inhibited by erythromycin < or =0.5 mg/L. Only one strain of C. jejuni was highly resistant to this antimicrobial agent. Of the compounds tested, gentamicin was the most active in vitro. The in vitro activity of the other antibiotics tested was variable. A quinolone could be a good choice for treating gastrointestinal infections when antimicrobial therapy is indicated. For C. jejuni, another antibiotic such as erythromycin should be considered.