During 2002-2004, a survey of entomopathogenic nematodes was conducted for the first time in Iran throughout the three provinces in the north-west of the country. Soil samples were tested for the presence of steinernematid and heterorhabditid nematodes by baiting with Galleria mellonella larvae. Of the 833 soil samples studied 27 were positive for entomopathogenic nematodes (3.2%), with 17 (2.0%) containing Heterorhabditis and ten (1.2%) Steinernema isolates. Morphological and molecular studies were carried out to characterise isolates. The Heterorhabditis isolates were identified as Heterorhabditis bacteriophora and Steinernema as Steinernema carpocapsae, S. bicornutum and S. feltiae. Heterorhabditis bacteriophora was the most common species, which was isolated from 17 sites across the three provinces. Steinernema feltiae was the most common species of Steinernema, which was isolated from eight sites but in only two provinces. Steinernema carpocapsae and S. bicornutum were each isolated from only one site. Steinernema spp. were isolated mainly from orchards and grasslands but Heterorhabditis was isolated mainly from grasslands and alfalfa fields.