OBJECTIVE: To validate the Reflux Symptom Index (RSI) in Greek patients and estimate the prevalence of laryngopharyngeal reflux (LPR) symptoms in the Greek population.STUDY DESIGN: Prospective, controlled validation study.SETTING: Tertiary referral hospital and primary care.SUBJECTS AND METHODS: For validation purposes, the instrument was administered to 53 patients with confirmed LPR. Sex- and age-matched controls with no LPR or gastroesophageal reflux disease (GERD) symptoms presenting in a primary care setting composed the control group. Reliability and construct validity were statistically appraised. Using the RSI, the authors estimated the prevalence of LPR in a randomly selected sample of the Greek adult population.RESULTS: The mean (SD) RSI score of the 172 sex- and age-matched controls was 3.2 (3.5). The mean (SD) RSI score of the 53 confirmed LPR patients was 19.9 (6.8). Cronbach α was 0.865. Factor analysis verified that the RSI instrument consists of 2 principal factors. To estimate the prevalence of LPR, a representative sample of the Greek adult population (188 subjects) completed the RSI questionnaire: 36.3% were male, and 29.6% were smokers. Mean (SD) age was 53.4 (17.7) years. The instrument was able to discriminate 16 patients with LPR symptoms with a mean (SD) score of 18.91 (6.39).CONCLUSION: The authors evaluated the internal consistency, reliability, and construct validity of the RSI for the Greek population. Factor analysis of the Greek translation of the RSI demonstrated that it can be a reliable tool in the diagnostic approach of LPR patients. Using the RSI, the authors recorded that the prevalence of LPR in a representative sample of the Greek population is 8.5%.