Thirty-four fungal isolates of Beauveria bassiana (Balsamo) Vuillemin (Hyphomycete: Deuteromycetes) and two isolates of Paecilomyces lilacinus were evaluated in vitro for their entomopathogenic activity against larval and adult house fly, Musca domestica L. (Diptera: Muscidae). Of the fungal isolates tested, B. bassiana isolates were pathogenic to adult flies, causing mortality levels of 30–100 % within six days. The P. lilacinus isolates were non-pathogenic towards adult flies. All the fungal isolates were marginally effective in controlling house fly larvae except isolates of P.lilacinus. Four B. bassiana isolates that caused mortality of 90 % or more within two days were subjected to dose-response mortality bioassays. The lethal concentration of B. bassiana isolates that caused 50 % mortality (LC₅₀) ranged between 10³–10⁵ conidia/ml. The lethal time to 50 % mortality (LT₅₀) values ranged between 0.44–1.3 days.