The species of Diheterospora attacking bdelloid rotifers have been compared with Diheterospora chlamydosporia and found to be different in a number of important characteristics. These include the consistent presence of aphanophialides, proliferation of phialides and aphanophialides to form polyphialides, containment of the conidial mass in a hydrophobic membrane, reduction or elimination of the verticillate arrangement of the conidiogenous cells, and presence of a large oil droplet in each conidium. It is considered that these differences are sufficient to separate the rotifer parasites from both Diheterospora and Verticillium. Accordingly, a new genus, Rotiferophthora, is erected to accommodate the 17 species recognized in this group of fungi. Thirteen rotifer parasites previously described under Diheterospora, Verticillium, or Acrostalagmus are transferred to Rotiferophthora, and four new species of Rotiferophthora are described. Key words: Diheterospora, Rotiferophthora, endoparasite, rotifer.