We have analysed the incidence and risk factors for the occurrence of invasive fungal infections (IFI) among 395 recipients of an allogeneic peripheral blood stem cell transplantation (PBSCT) from a human leucocyte antigen (HLA)-identical sibling. IFI (n = 50) occurred in 46 patients, giving an overall probability of 14%. There were 12 cases of invasive candidiasis (3%), with only one death. Non-Candida IFI occurred in 37 patients (12% probability), mostly invasive aspergillosis (n = 32). In multivariate analysis the only two significant variables associated with a higher risk of developing a non-Candida IFI were the development of moderate-to-severe graft-versus-host disease (GvHD, P < 0.0001; OR 4.6) and having received steroid prophylaxis for GvHD (P = 0.04; OR 2.1). In multivariate analysis the variables associated with a lower overall survival after PBSCT were development of a non-Candida IFI (P < 0.0001; OR 5.6), non-early disease phase (P = 0.0001; OR 1.9), steroid prophylaxis (P = 0.02; OR 1.4), moderate-to-severe GvHD (P = 0.01; OR 1.6) and cytomegalovirus infection post transplant (P = 0.001; OR 1.8). Our results show that non-Candida IFI (in particular aspergillosis) was an important cause of infectious morbidity and mortality after an HLA-identical sibling PBSCT, while invasive candidiasis was rare. Use of steroid prophylaxis and, in particular, the development of moderate-to-severe GvHD post transplant were risk factors for non-Candida IFI. Prophylactic strategies for these infections should thus take into account these risk factors.