The 35 full-length Borrelia burgdorferi sensu lato complex a83/100 gene nucleotide sequences were determined. High level of homology was observed in the nucleotide sequences corresponding to the strains and isolates of Borrelia fzelii. The analysis of the nucleotide sequences revealed two groups of Borrelia garinii. The most variable p83/100 gene region containing species-typical insertions and deletions was demonstrated to be included into the region where the antigenic determinants of protein were encoded. According to the data obtained in this work, the modification of the P83/100 protein structure and immunological properties could be suggested to exist even within species. The results of this work could be used for receiving recombinant P83/100 proteins useful for diagnostic applications.