Soil surveys were conducted in Ireland and Britain for Heterorhabditis nematodes. Soil samples taken from sandy locations were baited with Galleria rnellonella larvae. Heterorhabditis was detected at 18/169 sites in Ireland, 21.5 1 sites in the North of Scotland, and 9/20 sites in the South of Wales. All of the positive sites were coastal; the genus was not detected at any of the 40 inland sites sampled. All of the 76 isolates recovered in these surveys were identified, using isoelectric focusing, DNA estriction and cross-breeding methods, as belonging to the Irish Group of Heterorhabditis. No member of the North-West European Group of Heterorhabditis was recovered. However, an isolate recovered by other workers and originating in the south of England was identified as belonging to that group. Members of the Irish Group did not generally interbreed with embers of the "E Group from either England or continental Europe, though fertile infective juveniles resulted in a minority (3/15) of intergroup crosses.