Abstract: Laboratory bioassays were conducted in order to evaluate the efficacy of Iranian isolates of entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metsch.) Sorokin against adults of the lesser grain borer, Rhyzopertha dominica (F.) on stored wheat. All the isolates tested were pathogenic to the beetle although mortality rates were different between them. The cumulative mortality after treatment varied from 14.78% in M. anisopliae DEMI001 at low concentration (1.5x104 conidia mL-1) to 89.35% in B. bassiana Iran 441C at the highest concentration (1x1010 conidia mL-1). Probit analysis showed that the lowest LC50 values were 9.6x105 and 1.9x107 (conidia mL-1) for B. bassiana Iran 187C and M. anisopliae DEMI001, respectively. The values of LT50 varied from 6.77 to 9.28 days for B. bassiana isolates, and from 7.48 to 8.25 days for M. anisopliae isolates.