The study was conducted to examine the biodiversity of terrestrial nematodes in agricultural and non-agricultural areas of Sanliurfa, Turkey. Study area defined with the semi-arid features consisting irrigated and dry cultures, has been divided into 5 sub-regions regarding the geographic and ecological boundaries. Samples were taken twice a year, one in the mid-spring and second in the mid-fall for 3 years, in 2003-2005.

Nematode fauna has been represented by 26 species, 28 genus, and 4 families which all belonged to 8 orders. The proportions of plant parasitic and free-living nematodes were 39 % and 61%, respectively. Plant parasitic nematodes were represented by 26 species and 6 genera belonged to 2 orders (Tylenchida and Dorylaimida); bacterivores were represented by 4 families and 10 genus belonged to 4 orders (Rhabditida, Cephalobida, Diplogaterida and Monhysterida); fungivores were represented by 3 genus belonged to 2 orders (Aphelenchida and Tylenchida); predators were represented by 2 genus belonged to 2 orders (Mononchida and Aphelenchida) and the omnivores repsetented by 7 genus belonged to 1 order (Dorylaimida). Diversity of nematode communities either in the plant parasitic fauna or the free-living fauna have displayed differences in the sub-regions of the study area. The main reason may be due to the past history of the agricultural practices employed in each of the sub-regions.