Functional differences and association with inflammatory disorders were found relating to three major haptoglobin (Hp) phenotypes. Our aim was to investigate Hp polymorphisms in Hungarian patients with Crohn's disease (CD). Four hundred sixty-eight CD patients and 384 healthy controls were examined. Hp phenotypes were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting of the sera. The frequency of the Hp(1) allele was significantly higher in CD (0.395; OR, 1.24; 95% CI, 1.02-1.52; P=0.03) compared to controls (0.345). In CD, Hp phenotype was associated with disease behavior (OR [Hp(2-1) vs other], 2.06; 95% CI, 1.29-3.28 for inflammatory behavior). Furthermore, an increased frequency of primary sclerosing cholangitis was observed in the Hp 2-2 compared to the Hp 1-1 phenotype (6.5% vs. 0.0%; P=0.039). We conclude that the Hp polymorphism is associated with CD, inflammatory disease behavior, and primary sclerosing cholangitis in Hungarian patients. Further studies are required to evaluate the significance of Hp polymorphisms in other populations from geographically diverse regions.