The growth of three entomopathogenic fungi, Verticillium lecanii, Beauveria bassiana, and Metarhizium anisopliae, was determined in a yeast extract – peptone – dextrose (YPD) medium or a defined medium supplemented with dihydro-xyphenylalanine, dopamine, dopamine-HCl, norepinephrine-HCl, dihydroxyphenylacetic acid, or catechol. These diphenols may be found as part of the insect cuticle or hemolymph. Without diphenols YPD medium afforded generally higher growth of the fungi when compared with defined medium. Least growth was observed for B. bassiana and M. anisopliae in defined medium supplemented with dopamine, dopamine-HCl, or norepinephrine-HCl. Best growth for B. bassiana and M. anisopliae in defined medium was observed in unsupplemented medium or medium supplemented with dihydroxyphenylacetic acid, dihydroxyphenylalanine, or catechol. Best growth for V. lecanii was observed in a defined medium supplemented with dopamine, dopamine-HCl, or norepinephrine-HCl. In YPD medium, catechol inhibited growth of B. bassiana and M. anisopliae, whereas dihydroxyphenylalanine stimulated growth. The results showed similarities in M. anisopliae and B. bassiana response to various diphenols, whereas V. lecanii was different. Key words: diphenols, entomopathogenic fungi, Beauveria bassiana, Metarhizium anisopliae, Verticillium lecanii, fungal growth.