Certain cytokine gene polymorphisms may be associated with severe acute graft-versus-host disease (GVHD) after allogeneic stem cell transplantation. The present study analysed 196 patients and their donors for TNF-308, TNFd, IL-10-1064 and IL-10-1082 gene polymorphisms. Serum analysis of tumour necrosis factor-alpha (TNF-alpha) and interleukin 10 (IL-10) levels during conditioning therapy was also performed. Among patients with sibling donors, the TNFd allele 4 was significantly correlated with acute GVHD grades II-IV (P < 0.01). Acute GVHD grades II-IV were more common among patients homozygous for the IL-10-1064 allele 13 (P = 0.02). Patients homozygous for the TNF-308 allele (AA) correlated with higher TNF-alpha serum levels during conditioning (P = 0.02).