BACKGROUND/AIMS: Ambulatory 24-hour dual probe pH monitoring, the reflux symptom index (RSI), and the reflux finding score (RFS) have been developed to standardize the diagnosis of laryngopharyngeal reflux (LPR). The aims of this study were to evaluate the relationship between the RSI and the ambulatory 24-hour dual probe pH monitoring, and we also wanted to investigate the sensitivity of pH monitoring in those patients with suspected LPR who were diagnosed by an empirical trial wtih proton pump inhibitor (PPI). METHODS: Forty six patients suffering with LPR symptoms were examined using the RSI, a laryngoscope and ambulatory 24-hour dual probe pH monitoring. RESULTS: LPR on pH monitoring occurred in 30 of the patients (65.2%) among those patients who were suspected of having LPR, based on the RSI or the RFS. There was a significant difference in the RSI between the patients with reflux and patients without reflux on the pH monitoring. The sensitivity and specificity of pH monitoring were 59.4% and 33.3%, respectively, based on 50% symptom improvement as determined by a trial with PPI. CONCLUSIONS: Ambulatory 24-hour dual probe pH monitoring is still useful, but it has a low sensitivity. Therefore, other diagnostic LPR criteria are needed to increase sensitivity of ambulatory 24-hour dual probe pH monitoring.