OBJECTIVE Intravenous proton pump inhibitors (PPIs) induce a high intragastric pH and may thereby improve haemostasis in patients with bleeding peptic ulcer. The aim of this study was to investigate whether a similar therapeutic intragastric pH level could be reached when the PPI was administered orally. METHODS Twenty-four-hour intragastric pH was measured in patients treated endoscopically for bleeding peptic ulcer (Forrest class I or II). The patients received lansoprazole capsules (90 mg) after successful endoscopic treatment, followed by 30 mg every third hour for 72 h. The primary end-point was the percentage of the 0 to 24-h registration period with an intragastric pH of 6 or higher. Additionally, the total number of patients obtaining an intragastric pH above 6 for 80% or more of the 0 to 24-h period after start of treatment was evaluated. RESULTS Of the 14 patients included in the study (4 F, mean age 74 years, range 50-84 years), 10 patients had duodenal ulcer and 4 had gastric ulcer; median lowest Hgb: 8.9 mg/ml (range 5.8-12.4), blood transfusions: 2.7 SAG units (range 0-7). In the 0 to 24-h period, the median time duration of pH above 6 was 55% (range 6-99). One out of 14 patients (7%) reached a pH above 6 in at least 80% of this time period. CONCLUSIONS An increase in intragastric pH of therapeutic importance was reached with this oral medication regimen. However, there were large intra-individual differences. Treatment with oral lansoprazole may be a therapeutic alternative to intravenous administration of PPI.