The repetitive extragenic palindrome-based polymerase chain reaction was optimized for typing Listeria monocytogenes by 1) using the QlAamp method to increase the reproducibility of DNA isolation, 2) running PCR with three different DNA concentrations in parallel, 3) using antibody-protected therrnostable DNA polymerase to reduce non-specific priming, and 4) using an improved temperature programme to increase the amplification yield. When applied to 42 L. monocytogenes strains isolated from food in the Czech and Slovak republics during 1999-2000, profiles of 7-15 DNA fragments of 330-3,310 bp were amplified. Based on REP-profiles, strains (serotypes 1/2 and 4) could be divided into 12 groups.