The opportunistic human pathogenic fungus Aspergillus fumigatus (Af) causes the majority of cases of invasive aspergillosis. Because Af enters the human body through inhalation of airborne conidia, the interaction of conidia with the innate immune system (alveolar macrophages) plays a key role in the etiology of aspergillosis. Therefore, it is of central interest to investigate response mechanisms of alveolar macrophages upon interaction with Af. Here, it is demonstrate that Af inhibited host cell apoptosis of alveolar macrophages, one of the major defense immune effector cells against this pathogen. This unexpected result was due to inhibition of caspase 3 by a yet unknown mechanism.