A karyological study of 20 taxa (45 populations) of the genus Onobrychis Adans. from different geographic origins is presented. We found the two usual basic chromosome numbers in the genus, x = 7 and x = 8. In the group with x = 7, six diploid (2n = 14), 22 tetraploid (2n = 28) populations and in the group with x = 8, 17 diploid populations were found. Detailed karyotype analysis allows us to group the different populations and to postulate relationships among them.