The efficiency of entomopathogenic nematodes on the terrestrial snail,Theba pisana, was studied in the laboratory and under semi-field conditions.The percentage of mortalities were recorded when four nematode species, i.e., Heterorhabditis  indicus  (Hi),H. bacteriophora (Hb),H.bacteriophora (HP88),and Steinernema riobravis were used at 1000,2000, 3000,4000,and 5000 IJs/pot. The infected snails were observed for 8 days. At the highest inoculums level, H. indicus ,H.bacteriophora riobravis (Hb),H.bacteriophora (HP88)gave mortality percentages up to 100% after 4 days of infection, while the species S . riobravae (Sr)gave 65% mortality at the same inoculum levels and after the same time. No development of the nematodes occurred inside the cadavers of snails. In addition, all cadavers were decomposed completely. In the semi field test, two species ,H. indicus and S. glaseri were sprayed on colonies of snails Theba pisana on the tree branches at three inoculum levels (1000,2000,3000 IJs/ml)with direct spraying. No mortalities were obtained at the two lower concentrations of both species. At the highest level (3000IJs/ml), H. indicus(Hi) gave 57.89% mortality after 3days of application only in the small individuals which ranged between 2-7mm. in length, while S. glaseri(Sg) gave 77.27% after the same time, and same inoculum level.