Invasive aspergillosis (IA) is a serious complication in patients undergoing allogeneic haematopoietic stem cell transplantation (HSCT), particularly from donors other than HLA-identical sibling. All 306 patients who underwent alternative donor HSCT between 01 January 1999 and 31 December 2006 were studied. Late IA was defined as occurring >or=40 days after HSCT. The median follow-up was 284 days (range, 1-2709). Donors were matched unrelated (n=185), mismatched related (n=69), mismatched unrelated (n=35) and unrelated cord blood (n=17). According to European Organization for Research and Treatment of Cancer/Mycoses Study Group criteria, 2 patients already had IA at HSCT, 23 had early IA and 20 had late IA (IA incidence 15%). Eight patients had proven and 37 probable IA. Multivariate analyses showed that significant predictors of IA were delayed neutrophil engraftment, extensive chronic GVHD (cGVHD), secondary neutropenia and relapse after transplant. Early IA was associated with active malignancy at HSCT, CMV reactivation and delayed lymphocyte engraftment. Late IA was predicted by cGVHD, steroid therapy, secondary neutropenia and relapse after HSCT. IA-related mortality among IA patients was 67% and was influenced by use of anti-thymocyte globulin, steroids, higher levels of creatinine, and lower levels of IgA and platelets. The outcome of IA depends on the severity of immunodeficiency and the status of the underlying disease.