Twenty-four-hour esophageal pH monitoring is useful for the quantitative measurement of gastroesophageal reflux and for the demonstration of a temporal relationship between symptoms and reflux. The symptom index, a numerical score, was developed to quantify the association between symptoms and reflux. Because the symptom index primarily assesses the specificity of a patient's reflux symptoms, we propose to refer to this score as the symptom specificity index. Because of certain limitations of this score, we developed and evaluated a new score, the symptom sensitivity index, that quantifies the subject's sensitivity for reflux. Fifty-two consecutive patients, referred to our laboratory for ambulatory 24-h pH recording were studied. Beside the conventional reflux variables, both indexes were calculated. Although a statistically significant correlation between the indexes was found, discordance between the specificity and sensitivity indexes was seen in 17 patients (33%). Based on the findings in this study we advocate that the symptom sensitivity index should be used, in addition to the symptom specificity index, and incorporated in future pH studies to optimalize the interpretation of the results.