Behçet's disease (BD) is a multisystem inflammatory disorder of unknown etiology, and infections with different microorganisms including streptococci have been claimed as triggers of inflammatory attacks in BD pathogenesis. Toll-like receptor 2 (TLR2) has been known to recognize several microbial antigens including that of streptococci, and TLR2 gene Arg753Gln polymorphism has been reported to be strongly associated with acute rheumatic fever with an odds ratio of 100. This study aimed to investigate the TLR2 gene Arg753Gln polymorphism in a group of patients with BD and rheumatic heart disease (RHD) and to analyze the role of genotyping errors resulting from duplicated gene segments. The study group consisted of 211 patients with BD, 95 patients with RHD, and 94 matched Turkish healthy controls. Because of the duplicated exon 3 in 23-kb upstream of the TLR2 gene, genotyping for the Arg753Gln polymorphism with polymerase chain reaction-restriction fragment length polymorphism method was carried out using a new set of primers and PstI restriction enzyme. TLR2 gene Gln753 allele was observed in two of 211 (1.0%) patients with BD, five of 95 (5.3%) patients with RHD, and two of 94 (2.1%) healthy controls. All patients and controls were found to be heterozygous for Arg753Gln polymorphism, except one patient with BD, who was homozygous for Gln753. Although a slight increase of heterozygosity was noted in patients with RHD, no statistically significant difference was observed in the distribution of Arg753Gln polymorphism in BD and RHD compared to healthy controls. In conclusion, TLR2 gene Arg753Gln polymorphism is not associated with BD nor with RHD; and a duplicated region of the TLR2 exon 3 located 23-kb upstream of the polymorphic region may explain contradictory association findings described so far. © 2009 Clinical Rheumatology.