We herein describe a patient with a Pseudallescheria boydii fungus ball in a tuberculous lung cavity, which was successfully treated four years earlier. The patient was HIV positive classified as C3 with a previous history of i.v. heroin abuse. The clinical presumptive diagnosis was radiologically established combined with histological examination. Culture of tissue confirmed and proved the fungal etiology. In vitro MIC values for voriconazole (0.5 mg/ml) guided antifungal prophylactic treatment before surgical eradication of the fungus ball since the patient was immunosuppressed. We discuss the clinical spectrum of P. boydii infections and currently medical approach.