Immunosuppression due to antineoplastic drugs or malignant tumor leaves patients extremely vulnerable to infection. Opportunistic fungi that rarely infect healthy persons can have very severe consequences in these patients. Candida albicans is the pathogen found most often, but several other Candida species may cause infection as well. Aspergillosis is the second most frequently seen fungal infection of the face and mouth in patients receiving chemotherapy. Less commonly seen but equally dangerous are infections with Torulopsis glabrata, Mucor, Absidia, Rhizopus oryzae, Histoplasma capsulatum, Cryptococcus neoformans, Coccidioides immitis, Fusarium species, and Trichosporon cutaneum. Restoration of impaired host defenses and use of nystatin (Mycostatin, Nilstat, O-V Statin), clotrimazole (Mycelex), amphotericin B (Fungizone Intravenous), and flucytosine (Ancobon) when appropriate are methods of control.