Introduction and Aims: Gastroesophageal reflux disease (GERD) is very common in western countries. GERD is increasing, has profound effects on health economics, disturbs the patient's health-related quality of life, and increases the risk for development of esophageal adenocarcinoma. GERD is considered to be infrequent in developing countries. This study was performed to determine the prevalence of GERD among Iranians.Materials and Methods: Major GERD symptoms (heartburn and acid regurgitation) were assessed through an interview by trained general practitioners in three different Iranian populations in 2002: Tehran University freshmen (n=3008), healthy blood donors in Tehran (n=3517), and participants in Golestan cohort study on esophageal carcinoma in Gonbad, north-east of Iran (n=1066). Presence of heartburn or acid regurgitation was considered as GERD and their frequencies were calculated during the last 12 months prior to recruitment.Results: Three episodes per week or more of GERD symptoms were recorded in 2.1% of university freshmen (mean age 19.1±2.1 years), 4.7% of blood donors (mean age 37.3±10.8 years), and 18.4% of the cohort study participants (mean age 51.3 ± 11.7 years). One to two episodes of GERD symptoms a week were reported in 5.1% of the university freshmen, 5.6% of blood donors and 12.7% of the cohort study participants.Conclusions: GERD symptoms are frequent among Iranians. There was also a trend toward increasing frequency of GERD with increasing age. A GERD symptom is more prevalent in Iran than other Asian countries and is comparable to that of western countries.