Objective: There is abundant opportunity for house fly, Musca domestica, to become contaminated and, in turn, to contaminate the patient environment. This study has been conducted with the aim of isolating and identifying the probable pathogenic inoculations of the flies in three hospitals in Ahwaz County, Khuzestan province, south-west of Iran. Methods: Adult flies were collected by means of insect net and then transferrs to lab for microbiological process.Results:Totally on all house fly samples the bacteria genus Pseudomonas and Esherichia coli had the significantly highest rate of infection (P<0.05). The genera Klebsiella, Bacillus, and Diphtroid has significant lowest rate of infection. Hot and humid weather of the Khuzestan province which is host of patients coming from far localities for hospitalization, provide suitable conditions for housefly activities during the year. Conclusions: Thus suitable and applicable control methods such as environmental sanitations should be implemented for hospital environment in Ahwaz County.