The minimum inhibitory concentrations of metronidazole and clarithromycin were determined for 780 Helicobacter pylori strains collected in 1994 and 1995 from three different regions in The Netherlands. The overall prevalence of primary metronidazole resistance was 17%, with resistance found more frequently in women (24%) than in men (13%). There was no significant difference between the levels of resistance in the three regions. Primary clarithromycin resistance was rare (1%) and relatively infrequent as compared to that found in other countries. Four of the six strains resistant to clarithromycin were also resistant to metronidazole.