SUMMARYA new species ofEurotiumis described asE. heterocaryoticum, isolated from rough rice (Oryza sativaL.) stored for 1–2 months at moisture contents between 14 and 15%. The conidial state is a newAspergillus, described asA. heterocaryoticus.The fungus is osmophilic and exists in two color phases, one with white conidial heads and the other with medium to dark brown conidial heads. Heterocaryosis between the two types is common in culture.