We have examined the antiviral activity of a crude extract prepared from the culture medium of the fungus Metarhizium anisopliae. Eight active destruxins were identified which showed strong suppressive effect on the production of the hepatitis B surface antigen (HBsAg) in human hepatoma Hep3B cells. One new compound, desmethyldestruxin B2 [1], was isolated from M. anisopliae. This structure was determined based on its nmr and mass spectral data.