Several studies have demonstrated that radiofrequency energy delivery at the gastroesophageal junction (the Stretta procedure) induces symptom relief in gastroesophageal reflux disease (GERD), although improvement of acid exposure on pH monitoring was usually limited. A role for decreased esophageal sensitivity has been suggested. Our aim was to evaluate the influence of Stretta on symptoms, acid exposure, and sensitivity to esophageal acid perfusion in GERD. Thirteen patients with established proton pump inhibitor (PPI)-dependent GERD (three males; mean age, 51+/-10 years) participated in the study. Before and 6 months after the procedure symptom score, pH monitoring and Bernstein acid perfusion test were performed. The latter was done by infusing HCl (pH 0.1) at a rate of 6 ml/min 15 cm proximal to the gastroesophageal junction for a maximum of 30 min or until the patients experienced heartburn. Results were compared by Student's t-test. Stretta procedure time was 51+/-4 min and no complications occurred. After 6 months, the symptom score was significantly improved (12.5+/-2.0 to 7.5+/-2.1; P<0.05), seven patients no longer needed daily PPI, and acid exposure was significantly decreased (11.6%+/-1.6% to 8.5%+/-1.8% of time pH<4; P<0.05). The time needed to induce heartburn during acid perfusion decreased from 9.5+/-2.3 to 18.1+/-3.4 min (P=0.01), and five patients became insensitive to 30-min acid perfusion, versus none at baseline (P=0.04). In conclusion, the Stretta procedure induces subjective improvement of GERD symptoms and decreases esophageal acid exposure. In addition, esophageal acid sensitivity is decreased 6 months after the Stretta procedure. The mechanism underlying this finding and its relevance to symptom control require further studies.