BACKGROUND: The development of well-tolerated acid suppressant drugs has stimulated substantial growth in the number of trials assessing therapy options for gastro-oesophageal reflux disease (GERD). AIM: To develop consensus statements to inform clinical trial design in adult patients with GERD. METHODS: Draft statements were developed employing a systematic literature review. A modified Delphi process including three rounds of voting was used to reach consensus. Between voting, statements were revised based on feedback from the Working Group and additional literature reviews. The final vote was at a face-to-face meeting that included discussion time. Voting was conducted using a six-point scale. RESULTS: At the last vote, 93% of the final 102 statements achieved consensus (defined a priori as being supported by >or=75% of the votes). The Working Group strongly supported the development of validated patient-reported outcome instruments. Symptom assessments carried out by the investigator were considered unacceptable. There was agreement that exclusion from clinical trials should be minimized to improve generalizability, that prospective evaluation ideally requires electronic timed/dated methods and that endoscopists should be blinded to patient symptom status. CONCLUSIONS: Implementation of the consensus statements will improve the quality and comparability of trials, and make them compatible with regulatory requirements.