Abstract: The efficiency of thirty bacterial strains to control leaf cotton worms (Spodopteralittoralis), was investigated. These bacterial strains were originally isolated from dead spinycotton bollworms (Erias insulana). Leaf cotton worms were fed for four days on castor bean(Ricinus communis) leaves (as a substitute to cotton leaves), which were soaked for 30 minutes insuspensions of four-days old bacterial cultures. The efficiency of bacterial species was relativelyhigh. About 19 strains killed over 10% of cotton leaf worms and ten of these strains were highlyoffensive, killing about 20-60% of leaf cotton worms. The most offensive strains (ten strains)were selected for further bacteriological studies. Preliminary characterization of the bacterialstrains revealed that all strains were gram positive rod-shaped with variable morphology. Eightstrains were identified as spore-forming species and two strains were gram-positive non-sporeformingrods. Some phenotypic tests (e.g., salt tolerance, heat tolerance, and some enzymaticactivities) were done. The spore-forming rods were related to the genera Bacillus andPaenibacillus. The results pointed out that the bacterial strains in this study could be goodcandidates for biological control of the destructive cotton pests (leaf worms and spiny or pinkbollworms) in Egypt.