An experiment was carried out in order to study, in laboratory condition, the pathogenicity of Beauveria brongniartii (strain LF-05) against Musca domestica. The conidia of B. brongniartii were obtained from Peru. The fungus was propagated in potato-dextrose-agar culture medium, and later in semi-crude sterilized rice. F 1 flies were obtained from wild specimens which were captured with mesh in a poultry breeding farm (Betijoque, Trujillo state, Venezuela). In the laboratory, one hundred and sixty adult flies from 3 days of age, divided into