To the Editor: We thank Dr Lin for his interest in our article and for the several points raised in his letter (1). Dr Lin's main concern is the fact that we did not check intragastric pH in our patients with bleeding peptic ulcers, given that the presumptive aim of pharmacological treatment in such cases is to increase intragastric pH above the proteolytic range of pepsin. In vitro, fibrin clots are dissolved when pH falls below 4, and platelet aggregation is totally inhibited when pH falls below 5.9. Previous evidence has sustained the claim that profound acid suppression is essential for a favorable outcome in peptic ulcer bleeding cases. Obviously, the in vitro–generated hypothesis that optimizing intragastric pH during acute peptic ulcer bleeding might reduce patients' risk of morbidity and mortality had to be validated in vivo. Indeed, all in vitro data represent only surrogate end points, whereas in vivo data are the essential outcome measures on which clinical decisions should be based. In our head-to-head comparison of standard bolus vs. an intensive regimen of proton pump inhibitor administration after successful endoscopic hemostasis, the former regimen proved as effective as the high-dose infusion in terms of preventing peptic ulcer rebleeding (2). A recent trial from Hong Kong reported results similar to ours (3). Ulcer healing is a complex process, and it is likely that factors in addition to high pH level contribute to the cessation of ulcer bleeding, as this usually occurs without intervention.