HIV-positive patients and those persons immunosuppressed as a result of other diseases or chemotherapy are especially susceptible to mycotic infections. The superficial fungal infections seen most often in patients with HIV infection include seborrheic dermatitis, various dermatophyte infections, candidiasis, and onychomycosis. Uncommonly, systemic fungal infections, such as candidiasis, histoplasmosis, cryptococcosis, and coccidioidomycosis, may disseminate to the skin, producing a wide variety of cutaneous lesions. All cutaneous lesions in these patients should be biopsied and cultured if any question exists regarding the diagnosis. The diagnosis of superficial and deep mycotic infections in HIV-positive patients can be particularly difficult because the clinical presentation varies greatly and is often atypical.