When the recently developed, internationally recognized IFIGC/MSG/EORTC diagnostic criteria were retrospectively applied to a consecutive series of acute leukemia patients, the overall frequency of IPA was 25,3% (proven/probable 8,5%; possible 16,9%). Criteria for a diagnosis of IPA were fulfilled in 62,8% of pulmonary infiltrates developing in AL patients (proven/probable 17,1%; possible 45,7%). IPA developed both in AML and in ALL patients. Proven/probable IPA developed in 83% of cases during the first induction cycle (Borlenghi, EHA 2003). It may be estimated that such figures would be higher when patients would be followed prospectively and strictly monitored, particularly with GM antigenemia.