The aim of this study was to investigate an association between the development of cholangiocarcinoma(CCA)and the ABO variant rs505922(known to increase pan-creatic cancer risk)in a large cohort of European individuals with CCA.In total,180 individuals with CCA and 350 CCA-free controls were included.The ABO variant rs505922 was genotyped using a polymerase chain reaction-based assay.Association between this single nucleotide polymorphism(SNP)and CCA was tested in contingency tables.Neither allele distributions nor association tests and regression analysis provided evidence for an increased risk of CCA among carriers of the ABO variant(all P > 0.05).Nevertheless,we documented a deviation from Hardy-Weinberg equilibrium in the entire CCA cohort(P = 0.028)and for patients with intrahe-patic(P = 0.037)but not extrahepatic tumor localization(P > 0.05).The association tests did not provide evidence for a prominent role of the investigated SNP in the genetic risk of CCA.However,Hardy-Weinberg disequilibrium in the entire cohort and the intrahepatic CCA subgroup warrants future studies investigating a potential CCA risk modulation by individual blood groups. The aim of this study was to investigate an association between the development of cholangiocarcinoma (CCA) and the ABO variant rs505922 (known to increase pan-creatic cancer risk) in a large cohort of European individuals with CCA. and 350 CCA-free controls were included. The ABO variant rs505922 was genotyped using a polymerase chain reaction-based assay. Association between this single nucleotide polymorphism (SNP) and CCA was tested in contingency tables. Neither allele distributions nor association tests and regression analysis provided evidence for an increased risk of CCA among carriers of the ABO variant (all P> 0.05) .Nevertheless, we documented a deviation from Hardy-Weinberg equilibrium in the entire CCA cohort (P = 0.028) and for patients with intrahepatic ( P> 0.037) but not extrahepatic tumor localization (P> 0.05). The association tests did not provide proof for a prominent role of the investigated SNP in the genetic risk of CCA. Still, Hardy-Weinber g disequilibrium in the entire cohort and the intrahepatic CCA subgroup warrants future studies investigating a potential CCA risk modulation by individual blood groups.