Aggressive fungal rhinosinusitis with Chrysosporium sp. occurred in a patient with acute lymphocytic leukemia. The infecting organism is an exceedingly rare human pathogen. Usually, human chrysosporial infections are mild and unmarked by symptoms. Most case reports appear in the pathology literature and describe the incidental finding of adiaspores in the pulmonary parenchyma at autopsy. Clinical disease from active growth of chrysosporial mycelia in human tissues has been noted on a porcine aortic valve prosthesis and in a tibial abscess. Hyphal elements were not recovered from any other body parts of these patients. Histopathologic and microbiologic studies permitted the identification of this rarely encountered organism. Our patient experienced systemic spread of Chrysosporium organisms. Treatment of this pathogen is the same as for other opportunistic fungal infections.