The morphological characteristics of two tropical clavicipitalean fungi on species of the plant family Asteraceae were examined. These species were found to be superficial on the stems of living plants but early stages of infection involve necrotrophy of scale insects. These fungi are distinct from other Clavicipitaceae by possession of anamorphs producing multiseptate conidia. A new genus, Hyperdermium , was proposed to accommodate these ttwo species. In cultures on potato dextrose agar overlaid with cellulose acetate sheets, both species produced colonies resembling those on plant tissues. Hyperdermium bertonii produced conidia in culture but not perithecia. Hyperdermium pulvinatum produced both conidia and perithecia in culture. Phylogenetic analysis using large subunit rDNA sequences placed Hyperdermium in the subfamily Cordycipitoideae. A study was made of perithecial ontogeny in H. pulvinatum. Centrum development was of the Epichloe-type.