Esophageal pH testing, first described more than 3 decades ago, has become incorporated in the diagnostic armamentarium of most gastroenterologists. Using commercially available sophisticated equipment and software, the procedure is easy to perform and the analysis of the signals is automated. Nevertheless, users of esophageal pH testing must remain aware of the technical pitfalls that may stand in the way of the acquisition of meaningful results. Esophageal pH monitoring provides quantitative information about the exposure of the distal esophagus to acid. The technique makes it also possible, however, to quantify the correlation between symptom episodes and reflux events. In clinical practice, the latter is often more relevant than information on esophageal acid exposure.