Reflux esophagitis is suspected on clinical grounds and confirmed by a variety of endoscopical, roentgenological and physiological investigations, which are obviously inapplicable to an epidemiological survey. Questionnaire for the diagnosis of reflux disease(QUEST) can reduce bias introduced by observer variability, is practical, inexpensive, and noninvasive. QUEST also has good sensitivity and specificity for reflux esophagitis, so it's one of the useful diagnostic tools for reflux esophagitis. It, however, needs to be modified for the diagnosis of gastroesophageal reflux disease (GERD). Questionnaires to measure Quality of Life(QOL) quantitatively can be applied to the assessment of the severity of diseases or drug efficacy, and they are useful especially for the evaluation of endoscopy-negative GERD.