In summary, GERD patients are usually well managed using a careful medical history, endoscopy, and empirical trials of antireflux medications. Extended esophageal pH monitoring is unnecessary in most patients but can be of considerable value in managing patients with typical or atypical symptoms who are refractory to standard therapy for GERD. Furthermore, the test can be useful in documenting abnormal reflux in an individual without esophagitis being evaluated for antireflux surgery. The test is done with compact, portable data loggers, miniature pH electrodes, and computerized data analysis. The pH electrode should be positioned 5 cm above the manometrically defined upper limit of the LES, and patients should undergo the test on an unrestricted diet. In terms of data analysis, the total percentage time of pH < 4 provides as much information as any other scheme of quantifying esophageal acid exposure, but symptom association is essential when evaluating atypical or sporadic symptoms. Enthusiasm for 24-h pH monitoring must, however, be tempered with an analysis of its proven clinical utility in patient management with its utility rightfully compared with that of an empirical trial of anti-reflux therapy. Ambulatory pH monitoring is probably most useful in examining patients without typical reflux symptoms or patients who have either partially or completely failed a trial of anti-reflux therapy. To date, there have not been any prospective, controlled clinical trials evaluating these uses. Suggested clinical indications for ambulatory pH monitoring are listed in Table 5 (53).