Efficacy of the two entomopathogenic nematode species, Heterorhabditis bacteriophora Poinar (HP88 strain) and Steirnema glaseri Steiner (NJ strain), was tested on the fifth and third instar larvaeof Spodoptera littoralis (Boisd.) and Temnorhynchus baal (Reiche) under laboratory conditions. Experiments were conducted on filter paper and sandy soil substrates using nematode at 50, 100, 200and 400 infective juveniles/5ml of water. Heterorhabditis bacteriophora was most effective on thefifth instar larvae of S. littoralis whereas S. glaseri was effective against third instar larvae of T. ball third. Insect mortality was high (60-90%) and low (<45%) at higher and lower nematodeconcentrations respectively. Heterorhabditis bacteriophora treated larvae of S. littoralis succumbedto the infection at the higher rates (80-100%) as compared to those treated with S. glaseri. The rate of mortality of S. littoralis was lowest when treated with S. glaseri (2-20%). The differences in the rateof nematode infection and insect mortality under various experimental conditions are attributed tothe difference in the behavior, virulence, rate of penetration and host searching abilities of nematodes and the abilities of insect pest larvae to resist nematode penetration. Present study suggests that entomopathogenic nematodes are important and effective biological control agents of most soil dwelling insect pests.