Two cases of disseminated systemic zygomycosis caused by Cunninghamella bertholletiae in compromised persons were studied. The underlying disease in one patient was hematopoietic dysplasia (preleukemic syndrome) and in the other, postnecrotic hepatic cirrhosis. A definitive diagnosis of zygomycosis caused by C bertholletiae is achieved only by isolation and identification of the fungus and by demonstration of tissue invasion.