This study examined chromosome numbers and karyotypes of four taxa, Hesperis novakii Dvorak, H. bottae Fourn., H. balansae Fourn. and H. syriaca (DC.) Dvorak, from naturally growing Diaplictos (Dvorak) Dvorak section, which is represented by only these four taxa in Turkey, in the genus Hesperis. H. novakii and H. syriaca have 2n=14 chromosomes, H. bottae and H. balansae have 2n=12 chromosomes in somatic cells. Total chromosome lengths are 5.37 mu m and 2.17 mu m in H. novakii, 5.38 mu m and 2.70 mu m in H. bottae, 9.59 mu m and 4.28 mu m in H. balansae, 4.88 mu m and 2.32 mu m in H. syriaca (no. 4969), 7.89 mu m and 3.44 mu m in H. syriaca (no. 4971). The karyotypes are as follows: H. novakii consists of 3m+1sm+1st+2T, H. bottae consists of 4m+2st, H. balansae consists of 4m+2sm, H. syriaca (no. 4969) consists of 3m+1sm+1st+2T and H. syriaca (no. 4971) consists of 3m+1sm+1st+2T chromosome pairs. Results were discussed from a cytological and taxonomical point of view.