Strains (107) of L. monocytogenes were tested with a PCR-restriction enzyme analysis with two new original primers. A segment of 1395 bp containing the entire iap gene in L. monocytogenes was amplified by the PCR technique. The PCR product was cleaved with the restriction enzymes HindIII and RsaI, and the fragments generated were separated by gel electrophoresis. Two groups of serovars were obtained: one group contained serovars 1/2a and 1/2c, the other group contained serovars 1/2b, 3b and 4b. The PCR-restriction enzyme analysis method described in this paper could be a useful tool for the unambiguous division of L. monocytogenes into two serovar groups, and it could be used to study the evolution of different serotypes and groups of serotypes in foods produced in the same processing plant and processed during the same month. The RE-PCR method used can give a rapid confirm at the subgroup level in the laboratory of an epidemiological association between human disease and suspected sources of contaminated food.