Resistance of Helicobacter pylori to clarithromycin is due to point mutations at position A2143 or A2144 of the rrnH 23S rRNA gene, each mutation creating an additional restriction site for BsaI or MboII. A procedure combining PCR and RFLP analysis was evaluated for detection of these mutations using primers specific for the 23S rRNA gene, and BsaI and MboII enzymes. All clarithromycin-resistant isolates (8/8), as defined by the MIC, were found to be resistant by PCR-RFLP. No clarithromycin-sensitive isolates (14/14) gave a positive reaction.