We tested the efficiency of a nasal spray of Amphotericin B (AmB) in leukemic patients, in an attempt to prevent pulmonary Aspergillosis. From January to July, 8 cases of invasive Aspergillosis (IA) in 19 new leukemic patients were identified. Between July and September 15 patients were treated by prophylactic nasal spray of AmB (daily dose 5 mg). Compliance was excellent, but nevertheless typical IA developed in 5 patients. We conclude that at the dosage used prophylactic administration of nasal spray of (AmB) does not prevent IA.