Objective To evaluate whether the gastroesophageal reflux disease (GERD) questionnaire (GerdQ) symptom score could reflect the acid exposure indicated by 24-hour esophageal pH monitoring in patients with GERD, and to further validate the clinical application value of GerdQ.Methods From November 2008 to March 2010, 134 GERD patients from outpatient department with heartburn and acid reflux symptoms were enrolled.All the patients had undergone endoscopy examination, 24-hour esophageal pH monitoring and GerdQ scoring.According to 24-hour esophageal pH monitoring result, acid exposure group and none acid exposure group was divided by the percentage of time that pH was lower than 4 over 4.2% or DeMeester score over 14.72, the difference of GerdQ score was assessed.The receiver operating characteristic (ROC) curve of GerdQ score was drawn according to DeMeester score and the percentage of time that pH was lower than 4 as the gold standard.With SPSS 17.0 statistical software, the ratio was compared with the u test and Chi-square test, comparison between groups with t test.Results The BMI of acid exposure group was higher than that of none acid exposure group(t= 2.365, P= 0.019).The GerdQ score of acid exposure group (8.51± 2.34) was significantly higher than that of none acid exposure group (6.67 ± 2.79), the difference was statistically significant (t = 4.002, P = 0.000) .ROC curve was drawn according to DeMeester score over 14.72 as gold standard; the area under curve (AUC) was 0.70.When the critical value of GerdQ score was 7.5, Youden index was up to 0.3365, the sensitivity of diagnosis was 0.6909 and specificity was 0.6454.The percentage of time that PH was lower than 4 over 4.2% as the gold standard, the AUC of GerdQ score was 0.663.When the critical value of GerdQ score was 7.5, Youden index was up to 0.2790, the sensitivity of diagnosis was 0.6600 and specificity was 0.6190.Conclusions GerdQ score greater than 7.5 can better reflect acid exposure at the lower esophageal.There is stronger association between GerdQ score with the DeMeester acid exposure score over 14.72 than with the percentage of time that pH lower than 4 over 4.2% as the critical value for acid exposure.Obesity may aggravate the transient lower esophageal sphincter relaxation leading to occurrence of GERD symptoms.