Entomopathogenic nematodes (EPNs) are commonly used as biological agents for control of insect pests. This study was carried out to identify EPNs, determine dominant and frequent species in Kurdistan province, Iran and characterize their symbiotic bacteria. Identification of EPNs was performed based on morphological and morphometrical characters and also rRNA-ITS gene sequences. Two EPNs, Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae) and Steinernema feltiae (Rhabditida:

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... matidae) were identified. Out of totally 150 soil samples collected mainly from mid-southern parts of the province, 60% were positive for EPNs. Heterorhabditis bacteriphora showed the highest frequency in this region, remarkably 59.3% of soil samples contained this species. Incidences of H. bacteriphora in grasslands, woodlands and alfalfa fields were 57.3, 14.6 and 28.0 percent, respectively. Steinernema feltiae was found only in alfalfa fields with 0.66% frequency. Bacterial symbionts of H. bacteriophora and S. feltiae were also identified based on biochemical characters and recA gene sequencing. In this research, two species of Photorhabdus were isolated from H. bacteriophora namely P. luminescens subsp. kayaii and P. temperata subsp. thracensis. Xenorhabdus bovienii was identified from infective juveniles of S. feltiae.