Infections caused by fungi of the genus Aspergillus have become a major and dangerous problem in the modern treatments of blood diseases using cytotoxic drugs. Invasive pulmonary aspergillosis is the usual clinical manifestation of the disease. The clinical signs, not very suggestive, are those of an infective pneumonia and localized radiological forms are initially more frequent in most cases. The extra pulmonary forms are frequent: nose and sinus, skin, bone, digestive, central nervous system are principal localisations; but all organs may be affected by the processus of dissemination. The proximal tracheobronchial localisations may be seen by fibroscopy in 20% of cases, associated to invasive pulmonary aspergillosis. Diagnosis rests on pathological data, but in many cases the only possible examinations are broncho-alveolar lavage and bronchial brushing. The positive results are a major test of diagnosis.