The integration host factor (IHF) is a sequence-specific, histone-like, multi-fun- ctional DNA-binding and -bending protein of Escherichia coli. Characterization and functional analysis of this protein has been carried out mainly in bacteriophage λ and other mobile genetic elements. In this paper we report data concerning the binding of IHF protein to the plasmid oripl5A region. IHF binds to the single site of the DNA fragment containing the oripl5A, as shown by the gel mobility shift assays and footprinting experiment. On the basis of the ihf consensus sequences published, we have been able to identify one sequence of putative ihf site into the oripl5A sequence with two mismatches in relation to the consensus sequence of Kur et al., 1989, Gene 81,1-15. One ihf binding site was also found in the oriColEl region sequence with three mismatches in relation to this consensus sequence.