To investigate potential associations between the -463 G/A myeloperoxidase (MPO) promoter polymorphism and susceptibility to, and clinical expression of, Behçet's disease (BD).One hundred and seventy-five Italian patients who satisfied the International Study Group criteria for BD and 235 healthy age- and sex-matched blood donors were genotyped for the -463 G/A promoter polymorphism of the MPO gene by molecular methods. The patients were subgrouped according to the presence or absence of clinical manifestations.The distribution of allele and genotype frequencies of the MPO -463A/G polymorphism did not differ significantly between the BD patients and the healthy controls. Carriers of the -463 A allele (A/A or A/G) [odds ratio (OR) 0.7, 95% confidence interval (CI) 0.5-1.1] and homozygosity for A allele (OR 0.3, 95% CI 0.1-1.3) were less frequent among BD patients than among the controls, but the difference was not statistically significant. No significant associations were found when BD patients with and those without clinical manifestations were compared.Our data suggest that the -463 G/A promoter polymorphism of the MPO gene is not associated with susceptibility to, and clinical expression of, BD in Italian patients.