Patients after allogeneic stem-cell transplantation (alloSCT) have an increased risk for invasive aspergillosis (IA). Here, recipients of an allograft with IA (n=81) or without IA (n=58) were screened for 84 single nucleotide polymorphisms in 18 immune relevant genes. We found 3 markers in chemokine (C-X-C motif) ligand 10 (CXCL10, 4q21, 11,101 C>T, P=.007; 1642 C<G, P=.003; -1101 A<G, P=.001) significantly associated with an increased risk of developing IA. Furthermore, immature dendritic cells (iDCs) exposed to Aspergillus fumigatus germlings showed markedly higher CXCL10 expression, if carrying the wild type genotype, compared with the "CGAG" high risk haplotype. In addition, serum from patients with proven/probable IA showed increased serum levels of CXCL10, compared with immunocompromised patients without IA. Thus, polymorphisms in CXCL10 determine chemokine secretion by iDCs upon exposure to A fumigatus and most likely thereby genetically determine the risk of IA after alloSCT.