INTRODUCTION: Increased duodenal acid exposure (DAE) is associated with ulcer and dyspeptic symptoms but our understanding is limited by cumbersome recording methods. We have recently shown that prolonged radiotelemetry pH monitoring (RpHM) in the duodenum is feasible. This study compared DAE in controls and patients with functional dyspepsia (FD) using RpHM. METHODS: FD and controls underwent 48-hour recording of DAE using endoclip-secured RpHM capsules in the distal duodenal bulb. Subjects were nil per os except for meals eaten twice daily. FD completed a 14-item symptom checklist. Sleep periods were determined from diaries. Meal periods were defined as the 3-hour period after meal initiation. RESULTS: Thirty-four FD and 25 controls were studied. Prolonged recordings were obtained in 32/34 FD and 17/25 controls. Reasons for incomplete recordings were capsule dislodgement (7), procedural complication (1), and suspected gastric prolapse of capsule (2). Within groups, pH values for recording periods did not differ. Between groups, FD had significantly lower mean pH values [median (25th to 75th percentile)] during meals [5.11 (4.44 to 5.59) vs. 5.63 (5.17 to 6.10); P=0.003] and upright periods [4.69 (3.92 to 5.64) vs. 5.35 (4.55 to 6.31); P=0.01] but not during sleep. Duodenal pH values did not correlate with symptoms except for complaints of inability to finish a meal with meal (r=-0.341; P=0.05) and sleep (r=-0.383; P=0.03) pH. CONCLUSIONS: RpHM allows for prolonged recording of DAE. FD have l greater DAE than controls during daytime and meal periods. DAE and symptoms are poorly associated. The association of DAE with inability to finish a meal is consistent with prior studies demonstrating impaired proximal stomach function after duodenal acidification.