Interleukin-1 alpha (IL-1alpha) is a pro-inflammatory cytokine that is implicated in the initiation/maintenance of graft-versus-host disease (GVHD) and the immune response to infection. A cytosine (C) to thymine (T) transition at position -889 is believed to influence gene transcription. A previous single institution study showed that the presence of at least one IL1A T allele in the donor was associated with improved survival after unrelated donor haematopoietic stem cell transplant and lower transplant-related mortality if the donor and recipient each possessed the IL1A T allele. The present study sought to confirm these results in a larger homogeneous population. Thus the study population included 426 patients older than 18 years with chronic myeloid leukaemia (CML), transplanted in first chronic phase and receiving a total body irradiation and cyclophosphamide preparative regimen. Donor recipient pairs were categorised into four groups according to the presence or absence of an IL1A T allele in the donor and recipient. There were no significant differences in patient, donor and transplant characteristics between the groups. We did not observe an association with IL-1alpha genotype in donor and/or recipient and transplant-outcome. These data suggest that the outcome of unrelated donor transplant for CML is not influenced by IL-1alpha genotype.