Goals: The aim of this study is to investigate whether there were any association between the 102 T/C and-1438 G/A polymorphisms of the 5-HT2A receptor gene and IBS, and abdominal pain, anxiety and depression. Background: Genes involved in serotonin (5-HT)metabolism are good candidates for the pathogenesis of irritable bowel syndrome (IBS). Recently, a silent polymorphism in the 5-HT2A receptor gene was identified that is defined by a T to C transition at position 102. Also, a novel G to A base change at position-1438 of the promoter region has been detected in 5-HT2A receptor gene. Study: Fifty-four patients with IBS diagnosed according to the Rome 1 criteria and 107 healthy individuals were included in the study. PCR was used to amplify a 468-bp (G→ A) and 342-bp (T→ C) fragment of genomic DNA containing the polymorphism. Hospital anxiety and depression scale was used to assess the risk of depression and anxiety. Severity of chronic abdominal pain was determined by visual analogue scale (VAS). Results: It was shown that there was a high incidence of homozygote C allele of the 102T/C polymorphism (22.2% ; OR: 7.89, P =0.04) and homozygote A allele of the-1438 G/A promoter region (37% ; OR: 11.14, P = 0.01) in patients with IBS.The risk of having an anxiety disorder was 83.3% in patients with C/C genotype, which was higher than other allele carrying patients, and overall mean (52.7% ). (x2 = 8.56, P = 0.014). The patients with T/T genotype had a VAS score of 54.93 ± 2.59 mm, which was significantly higher than that of the patients with other genotypes (p1= 0.02, p2 = 0.001). Conclusion: This study suggests that the patients with homozygote C allele of the 102 T/C polymorphism of the 5-HT2A receptor gene, have a high risk of IBS. On the other hand, T/T genotype of 102T/C polymorphism may be associated with more severe pain in patient with IBS. Goals: The aim of this study is to investigate whether there were any association between the 102 T / C and-1438 G / A polymorphisms of the 5-HT2A receptor gene and IBS, and abdominal pain, anxiety and depression. in, serotonin (5-HT) metabolism are good candidates for the pathogenesis of irritable bowel syndrome (IBS). Recently, a silent polymorphism in the 5-HT2A receptor gene was identified that is defined by a T to C transition at position 102. Also , a novel G to A base change at position-1438 of the promoter region has been detected in 5-HT2A receptor gene. Study: Fifty-four patients with IBS diagnosed according to the Rome 1 criteria and 107 healthy individuals were included in the study . PCR was used to amplify a 468-bp (G → A) and 342-bp (T → C) fragment of genomic DNA containing the polymorphism. Hospital anxiety and depression scale was used to assess the risk of depression and anxiety. Severity of chronic abdominal pain was determined by visual analogu Results: It was shown that there was a high incidence of homozygote C allele of the 102T / C polymorphism (22.2%; OR: 7.89, P = 0.04) and homozygote A allele of the-1438 G / A of patients with IBS.The risk of having an anxiety disorder was 83.3% in patients with C / C genotype, which was higher than other allele carrying patients, and overall mean ( (X2 = 8.56, P = 0.014). The patients with T / T genotype had a VAS score of 54.93 ± 2.59 mm, which was significantly higher than that of the patients with the other genotypes (p1 = 0.02, p2 = 0.001). Conclusion: This study suggests that the patients with homozygote C allele of the 102 T / C polymorphism of the 5-HT2A receptor gene, have a high risk of IBS. On the other hand, T / T genotype of 102T / C polymorphism may be associated with more severe pain in patient with IBS.