Background: Gastroesophageal reflux disease (GERD) is a common condition, with wide geographical differences worldwide. There are no epidemiological data on this disease for Uruguay. Objective: To estimate the prevalence of GERD in two adult populations in Uruguay (urban and hospital) through the Gastroesophageal reflux disease Questionnaire (GerdQ) questionnaire and evaluation of typical symptoms. Material and method: A descriptive, cross-sectional study was carried out through the use of two diagnostic methods administered in two settings: an urban and a hospital setting. The first method consisted of administration of the standardized GerdQ structured questionnaire and the other consisted of evaluating the typical symptoms of GERD. A total of 1141 persons from the urban population, with a mean age of 52 years (+/- 18 years), and 163 persons from a gastroenterology polyclinic, with a mean age of 53 years (+/- 16 years), were included. Results: The prevalence of GERD in Uruguay was 4.69%, (95% CI 2.92-6.46%) when the GerdQ questionnaire was used, but increased to 14.14% (95% CI 12.57-15.71) when only typical symptoms were considered. In the hospital sample, the prevalence was 11.66% (95% CI 6.42-16.89%) and 20.25% (95% CI 14.01-26.48), respectively. Conclusion: The prevalence obtained in the urban population of Uruguay with the GerdQ questionnaire in the symptomatic (hospital) population was more than double that in the general population, 11.66% and 4.69%, respectively. Evaluation of symptoms, pyrosis and/or regurgitation systematically yields a higher prevalence. Consensus on the definition of GERD and on the instrument used for its diagnosis are essential to interpret and compare epidemiological studies. (C) 2011 Elsevier Espana, S.L. and AEEH y AEG. All rights reserved.