Aspergillus fumigatus is a fungus of the genus Aspergillus. A. fumigatus is present in the environment worldwide and it is able to infect immunocompetent patients as well as in immuno compromise individuals. In immunocompetent patients a seroconversion or a significant titer increase indicates an Aspergillosis. Patients with an increased antibody titer have in most of the cases an allergic bronchopulmonary aspergillosis or a pulmonary aspergilloma. In immuno compromised patients such as transplant patients and people with AIDS or leukemia A. fumigatus causes in almost all cases a disseminated invasive Aspergillosis.