This is the first research on free-living terrestrial nematodes in order Dorylaimida not only in Yok Don National Park, but also for Tay Nguyen area. The research result has shown that 39 species of Dorylaimida were identified from Yok Don National Park, belong 22 genera, 11 families. In the total of 39 species were identified, 12 species are new records for the Vietnam's fauna, belong 8 genera 6 families (see more detail in the list of Dorylaimida species, with symbol (*) as a remark for new record). Especially, 4 genera such as Paractinolaimus (famify Actinolaimidae)
Dorylaimoides (family Mydonomidae)
Eudorylaimus and Microdorylaimus (family Qudsianematidae) are recorded for the first time for Vietnam's fauna. In addition, 13 species of free-living terrestrial nematodes in order Dorylaimida were identified in other areas from Vietnam in previous also they were recorded in Yok Don. However, there are still 14 species that were not identified due to not available references.