BACKGROUND: Although familial clustering of functional dyspepsia (FD) has been reported, the role of genetics in the susceptibility to FD is still not well understood. Several reports indicate an association between FD and G-protein beta3 (GNB3) subunit gene polymorphism (C825T); however, these studies had small sample sizes and the findings are inconclusive. In the present study we clarified the association between GNB3 gene polymorphism and dyspepsia in a large population of Japanese subjects who visited a hospital for annual health check-up. METHODS: Subjects with significant upper gastrointestinal findings were excluded. Subjects with dyspeptic symptoms were divided into either a postprandial distress syndrome (PDS) group or an epigastric pain syndrome (EPS) group according to the Rome III criteria. The presence of the GNB3 C825T polymorphism was then evaluated and logistic regression analysis was used to test all variables. RESULTS: The GNB3 genotype distribution in subjects without dyspepsia was 191 CC (25.1%), 368 TC (48.4%), and 202 TT (26.5%) and 17 CC (25.0%), 29 TC (42.6%), and 22 TT (32.4%) in subjects with dyspepsia. No significant correlation was found between the GNB3 825TT genotype and dyspepsia. However, the TT genotype was significantly associated with subjects with EPS-like symptoms (odds ratio (OR) = 2.00, 95% confidence interval (CI); 1.07-3.76) compared to the CT/CC genotype adjusted for gender and age. No significant correlation was found between GNB3 polymorphism and PDS-like symptoms (OR = 0.68, 95% CI; 0.31-1.51). With the exclusion of subjects with both EPS- and PDS-like symptoms, only the TT genotype was significantly associated with EPS-like symptoms (OR = 2.73, 95% CI; 1.23-5.91). CONCLUSION: The homozygous GNB3 825T allele influences the susceptibility to EPS-like dyspepsia.