Invasive aspergillosis has become a major cause of infection-related mortality in nonneutropenic patients after allogeneic stem cell transplantation (SCT). To assess the potential role of Aspergillusspecific T-cell responses for the successful control of invasive aspergillosis, lymphoproliferative responses to Aspergillus fumigatus antigens were studied in healthy individuals, patients with evidence of invasive aspergillosis, and patients late after allogeneic SCT.