Campylobacter pylori has been associated with the etiology of gastritis and duodenal ulcer. It has been shown that several drugs, among them a variety of antimicrobials, eliminate C. pylori from gastric mucosa at least for a time, resulting in an improvement of the patients' symptoms. The activity of 16 antimicrobials (ampicillin, cefazolin, cefuroxime, cefotaxime, imipenem, aztreonam, tigemonam, erythromycin, vancomycin, nalidixic acid, colistin , norfloxacin, ciprofloxacin, difloxacin, ofloxacin and perfloxacin) was tested against 30 clinical isolates of C. pylori. The antimicrobials showing the highest activity were ampicillin, imipenem and ciprofloxacin, followed by cefazolin, cefuroxime, cefotaxime, aztreonam, tigemonam, erythromycin and difloxacin. Nalidixic acid, colistin and vancomycin were virtually ineffective against C. pylori.