Histophotometric evaluation of the DNA content of the post-kinetic nuclei (lymphocytes) has been performed in 8 species of Palearctic Microchiroptera:Rhinolophus ferrumequinum, R. euryale, R. hipposideros, Miniopterus schreibersi, Pipistrellus savii, P. kuhli, Myotys myotisandM. capaccinii.The results obtained are compared with the known data (CAPANNA and CIVITELLI 1970) on the morphology of the karyotype of these species and are discussed whith a view to explaining the relationships between chromosome transformations and variations in DNA content.