The pathogenicity of two species of entomopathogenic fungi ,Beauveria bassiana and B.brongniaretii against Aphis gossypii was examined under laboratory conditions. Data revealed that pathogenicity effect on nymphs and adults were very high and varied according to the conidia concentrations and periods after infection . The LC₅₀ values of B.bassiana and B.brongniartii against adults were 2.443x10³ conidia /ml and 3.118x10³ conidia/ml respectively. Also, the LC₅₀ values of the tested entomopathogenic fungi against nymphs were 2.279x10³ conidia/ml and 1.955x10³ conidia/ml, respectively.The accumulative mortality percentages of A.gossypii after treatment with different concentrations of each pathogen at different time intervals were conducted.