Five Egyptian heterorhabditids and two imported steinernematids isolates were evaluated against engorged females of the cattle tick, Boophilus annulatus under laboratory conditions. All tested strains entomopathogenic nematodes (EPN) showed high pathogenicity against B. annulatus. The most virulent strains were Heterorhabditis sp. S1 and Heterorhabditis sp. EG1 recorded 100% mortality for all suspensions on the 4th day post treatment. LC50 values of Heterorhabditis indica RM1, Heterorhabditis sp. ISK1, H. bacteriophora TWF, Steinernema carpocapsae all strain and S. riobravae SR were 52, 63, 636, 2375, and 5700 IJs/ml, respectively. In field trials, two techniques; soaked-cotton ball and spraying with 2000 IJs/ml nematode suspensions were applied on cows infested by semi-fed females of B. annulatus. The treated ticks were dropped from their hosts within 12 h post infection.