OBJECTIVE The aim of this study was to investigate if the inheritance of specific polymorphisms of interleukin 1 (IL-1) A, IL-1B and IL-1 receptor antagonist (IL-1RN) genes could affect the susceptibility to Behçet's disease (BD). METHODS A total of 132 BD patients and 105 healthy controls were genotyped for IL-1A -889, IL-1B -511, -35, +5810, +5887, and IL-1RN +8006, +8061, +9589, +11,100 single nucleotide polymorphisms, and IL-1RN 86-bp variable number of tandem repeat polymorphism. chi 2-analysis was used to compare the allele and genotype frequencies of the cases and controls. IL-1A and IL-1B haplotypes were reconstructed using the Phase program. RESULTS Inheritance of the C allele of the IL-1A -889 polymorphism was associated with BD (OR=2.0, P=0.01) and inheritance of the IL-1A -889C/IL-1B +5887T haplotype was identified as an increased risk for BD. The IL-1A -889 and IL-1B +5887 CC/TT combined genotype was significantly more observed in BD cases than in controls (57.5 vs 38.1%, OR=2.2, P=0.003). No association with BD was found for other investigated polymorphisms in the IL-1B and IL-1RN genes. CONCLUSIONS Susceptibility to BD is increased in individuals carrying both the IL-1A -889C and IL-1B +5887T haplotype. Individuals who are both homozygous CC at IL-1A -889 and TT at IL-1B +5887 appear to have twice the risk of developing BD as individuals having other IL-1A -889/IL-1B +5887 genotypes.