From infected pink and spiny bollworm larvae, collected from Qualyobia Gover-norate, Egypt, 13 bacterial isolates belonging to 7 species were detected. The effi-ciency of these bacterial isolates was evaluated on newly hatched pink and spiny bollworm larvae. Three bacterial species, namely, Pseudomonas viridiflava, Serratia grimesii and Cellulomonas flavigena had no efficiency. Meanwhile, four other en-tomopathogenic isolates bacterial species, Pseudomonas pyrrocinia (A1), Serratia marcesens (M3), Serratia rubidaea (E3) and Bacillus thuringiensis (S2) had notice-able efficiency. The efficiency of these isolates was compared to two commercial products, Dipel 2X and Protecto. Biochemical studies showed differences in total proteins bands patterns in uninfected and infected larvae.