Leukotoxic potential of Aggregatibacter actinomycetemcomitans strains has been studied by the use of several methods, and results differ depending on the methods used. The aim of the present study was to perform a comprehensive examination of the leukotoxic potential of a collection of A. actinomycetemcomitans strains by use of three quantitative methods, Western blotting, ELISA, and mRNA expression assay and compare these results with previous data obtained by a cell lysis assay. A higher leukotoxic potential among JP2 genotype strains compared to non-JP2 genotype strains of A. actinomycetemcomitans was found by Western blotting, ELISA and mRNA expression assay. Leukotoxicity as determined by cell lysis assay showed a variation among strains examined, not only depending on being part of JP2 genotype vs. non-JP2 genotype group of A. actinomycetemcomitans. The leukotoxicity of A. actinomycetemcomitans strains as determined by cell lysis assay did not correspond to the leukotoxic potential of A. actinomycetemcomitans strains as determined by three quantitative methods. A comparison of the results obtained by ELISA and mRNA expression assay showed a reasonable correlation between these two methods. It seems important to use more than one method to assess the LtxA-related virulence capacity of A. actinomycetemcomitans in order to obtain comprehensive understanding of the leukotoxic potential of A. actinomycetemcomitans strains.