Successful treatment of Helicobacter pylori infection is becoming compromised by emerging resistance. We report the prevalence rates of H. pylori resistance to metronidazole, clarithromycin, amoxycillin, tetracycline and trovafloxacin in The Netherlands. A total of 231 H. pylori clinical isolates were collected throughout the country over a period of 6 months during 1997-1998. The MICs of the above-mentioned antibiotics were determined in a single laboratory. The overall percentage of resistance for clarithromycin and metronidazole was 1.7% and 21.2%, respectively. None of the strains was resistant to amoxycillin or tetracycline. The primary resistance rate of trovafloxacin was as high as 4.7%. Since trovafloxacin has not yet been introduced on to the Dutch market, the resistance is probably induced by the use of other quinolones. Our data indicate that treatment outcome would benefit from susceptibility testing before starting therapy, especially when prescribing metronidazole.