Invasive aspergillosis has been classically associated with certain risk factors: cytotoxic chemotherapy, prolonged neutropenia, corticosteroids, transplantation, AIDS. However, the literature is growing that this mycosis, particularly pulmonary aspergillosis, can be seen in patients lacking these factors. Many of the latter patients are in the intensive care unit. Other associated conditions include influenza, nonfungal pneumonia, chronic obstructive lung disease, immaturity, sepsis, liver failure, alcoholism, chronic granulomatous disease and surgery. Certain focal sites, such as sinusitis or cerebral aspergillosis, have additional risk factors. This emphasizes the potential importance of a positive culture for Aspergillus in the critically ill, the need for awareness about possible aspergillosis in patients lacking the classical risk factors, and readiness to proceed with appropriate diagnostic maneuvers.