Two par regions were localized within the structure of a small colicinogenic plasmid ColA. One of them functions at the expense of plasmid multimere resolution. Analysis of the nucleotide sequence of the region revealed the existence of essential homology with the par locus of plasmid ColE1. As compared to E. coli C600, the function of multimere forms' resolution of plasmid DNA in E. coli C is reduced or absent due to par regions of the ColE1 type. Par regions of various degrees of homology with the par locus of ColE1 were localized by Southern hybridization within the structure of colicinogenic plasmids ColN and ColD. The stabilization of the colicinogenic plasmids is believed to be also determined by the functioning of genes connected with the synthesis and action of colicin.