Diagnosis of invasive pulmonary aspergillosis (IPA) is often difficult. Recently, the European Organization for Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG) has proposed new criteria for the classification of invasive fungal infections. We have studied the clinical applicability of this classification in 22 patients with hematological malignancies who had IPA at autopsy. While alive, according to the EORTC/MSG criteria, only 2 patients were classified as having proven IPA, 6 as probable, 13 as possible, and 1 was unclassifiable. Of the patients, 64% had no microbiological or major clinical criteria before death. Although the EORTC/MSG criteria are an important step forward in the standardization of definitions used for IPA in clinical research studies, most patients who die with extensive lung disease only reach a level of possible or probable IPA during life, further highlighting that these guidelines should not be used for clinical decision-making.