Frequent and prolonged exposure of immunocompromised patients to a variety of environmental conditions has resulted in the recognition of infections with new fungal opportunists. Infections with fungi such as Fusarium species, Paecilomyces lilacinus, Acremonium species, Trichosporon beigelii, Blastoschizomyces capitatus, Malassezia furfur, Penicillium marneffei, Scedosporium prolificans, and other dematiaceous species have become significant problems in the treatment of immunocompromised hosts. This discussion addresses several issues of pathogenesis, epidemiology, diagnosis, and treatment with regard to these new opportunists, through a review of both general and specific concepts. The growing need for training in clinical mycology is also summarized.