Comparative molecular phylogenetic study using nrDNA internal transcribed spacer region (ITS) sequences was carried out on species from three Astragalus L. (Fabaceae) sections from Turkey (Old World species) and the New World. A total of 56 taxa (179 accessions) including 30 species from Incani DC., 15 species from Hypoglottidei DC. and 11 species from Dissitiflori DC. section were used in the current study. The total length of the ITS region was 642 bp with 56 (8.7 %) parsimony-informative and 9 insertion\deletion sites. The constructed phylogenetic tree suggested that the section Incani had the most conserved ITS region among the studied Astragalus sections, evolutionarily separated from other sections and monophyletic. Also, DNA sequences of several New World (Neo-) Astragalus species analyzed comparatively with those from the current study indicated that New World aneuploid species of Astragalus clearly formed a monophyletic group separated from the species of the Old World.