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For an investigation, and identification of virulence effect of fungal pathogens of rice striped stem borer, Chilo suppressalis, dead larvae were collected from different rice fields in Guilan province. For isolation of the entomopathogenic fungi, the infected larvae were sterilized by etanol 96% for 1 minute, followed by chlorax 3% for 1minute. Afrer this stage, they were rinsed three times in sterile water. The larvae were placed on wet sterile filter paper in petridishes and incubated in 25?2°C and relative humidity of 85?5% for mycelial growth and sporulation. The fungal colony was formed on dead larvae within 48-72 hours, and sporulation started after 5 to 7 days. The fungi appeared on larvae bodies in white or green coverings. For each fungus, monconidial and purification operation of isolates were carried out on PDA and SDAY media. The Fungi, Beauveria bassiana (Bals.) vuill. and Metarhizium anisopliae (Metch.) Sorok. were identified. In this trial spores of B. bassiana were hyaline, globose to subglobose (2-3.5 ? 2-3 µm), while spores of M. anisopliae cylindrical to oval, often slightly narrower in the middle, truncate at both ends, (3.5-9? 2-4 µm). Pathogenicity of two species studied by using concentration of (1×106) spores per ml. Sterile water was applied for 15-20 sec. by dipping method on 5th instar of larvae under laboratory conditions. The results revealed that mean mortalities and sporulation of larvae by B. bassiana and M. anisopliae were 75.55,71.11% and 67.44, 62.22% respectively. No significan difference was observed among treatments involving the two Fungi.