Prolonged intragastric pH monitoring is a valuable technique for evaluating head-to-head comparisons of the antisecretory effects of different pharmacologic agents, for studying the effects of higher doses of proton pump inhibitors (PPIs) on daytime and nighttime pH control, for evaluating the effects of dose timing in relation to a meal on the intragastric pH response to these antisecretory agents, and for examining interindividual variability in individual pH response to PPIs taken orally. Measuring intragastric pH has helped immeasurably in understanding the efficacy of PPIs and is especially useful in the clinical arena to guide the management of patients across the spectrum of gastroesophageal reflux disease.