OBJECTIVE: To evaluate the associations between abdominal obesity and gastro-oesophageal reflux disease (GORD), and their interactions with ethnicity and gender. DESIGN: A cross-sectional study. Participants completed detailed symptom questionnaires and underwent a standardised examination, including anthropometric measurements. SETTING: A large integrated healthcare system. PATIENTS: 80 110 members of the Kaiser Permanente multiphasic health check-up cohort. MAIN OUTCOME MEASURES: Gastro-oesophageal reflux-type symptoms. RESULTS: Recent reflux-type symptoms were present in 11% of the population. The multivariate OR for symptoms with an abdominal diameter (adjusted for body mass index (BMI)) of >/=26 vs <16.3 cm was 1.85 (95% CI 1.55 to 2.21) for the white population, 0.95 (95% CI 0.61 to 1.48) for the black population and 0.64 (95% CI 0.18 to 2.30) for Asians. The mean abdominal diameter was greater in men (22.0 cm, 95% CI 21.9 to 22.0) than in women (20.1 cm, 95% CI 20.0 to 20.1, p<0.01), but the risk of symptoms for any given diameter did not differ markedly by gender. The association between increasing BMI and symptoms was also much stronger among the white population than among the black population. The association between BMI and reflux-type symptoms was partially mediated through abdominal diameter. CONCLUSIONS: There was a consistent association between abdominal diameter (independent of BMI) and reflux-type symptoms in the white population, but no consistent associations in the black population or Asians. The BMI association was also strongest among the white population. These findings, combined with the increased prevalence of abdominal obesity in male subjects, suggest that an increased obesity may disproportionately increase GORD-type symptoms in the white population and in male subjects.