Sunn pest, Eurygaster integriceps Puton (Heteroptera: Scutelleridae), is one of the major wheat pest in Iran and neighboring countries. In order to control this pest, every year hundred of thousands hectares of wheat crop are sprayed with synthetic pesticides in Iran. Biocontrol, the use of living organisms as pest control agents, became an important alternative to the use of chemical pesticides and, therefore, a potential means of reducing pesticide use and its undesirable effects on human health and the environment. Especially, entomopathogenic fungi offer exciting possibilities as biocontrol agents because of their damaging effects on the target insect host and their ability to cause epizootics. So, in the current study, pathogencity of two isolates (M189, 4556) of Metarhiziurn anisopliae (Metschnikoff) with five concentrations (1x10(4), lx10(5), lx 10(6), 1x 10(7), 1x 10(8)) on adult Sunn pest was evaluated. Each treatment consisted of 30 adults that replicated three times. The adults were dipped in the conidia concentrations for about 10-15 seconds, then were taken and transfered to filter paper to drain off excess liquid. Controls were treated only with distilled water plus Tween 80 (0.02 % ). Treated adults were maintained in growth chamber (25+/-1 degrees C, RH 80+/-5 %) and mortality was recorded daily over two weeks. Probit analysis showed that LCso for M 189 and 4556 were 7.704x10(5) and 3.38x10(5), respectively. The results revealed that isolate 4556 was more effective on Sunn pest than the M189 isolate. Our results showed that different isolates of M. anisopliae have different effects on Sunn pest adult. So, identification, application and screening of different isolates in bioassays will provide a promising potential for finding of efficient isolate to be used in field studies as bio-pesticides.