The morphological and molecular characteristics of 41 populations of cereal cyst nematodes (Heterodera avenae group) collected in Adana, Osmaniye, Kahramanmaras, Hatay, Gaziantep, and Kilis provinces in the eastern Mediterranean region of Turkey were studied. The morphological characters and morphometric features of second-stage juveniles and cysts showed the presence of 3 Heterodera species: H. avenae, H. filipjevi, and H. latipons. All morphological values of these distinct populations were very similar to those previously described for these species. Genetic variation was observed among the identified cyst nematode species H. avenae, H. filipjevi, and H. latipons. Intraspecific polymorphism was observed within H. avenae and H. latipons but not in H. filipjevi populations. Molecular analysis using ITS regions of rDNA confirmed the identities of the 3 Heterodera species. According to our results, 75% of isolates were identified as H. avenae, 15% as H. latipons, and 10% as H. filipjevi.