Objective: The objective of this study was to evaluate the validity of the Heartburn Reflux Dyspepsia Questionnaire (HRDQ), a newly developed measure of gastro-oesophageal reflux disease (GORD) symptoms. Specifically, the HRDQ was developed for patients, who still experience symptoms with proton pump inhibitor (PPI) treatment. Material and methods: The psychometric properties of HRDQ were evaluated based on data from two clinical trials of patients with GORD with a partial response to PPIs, one from the UK and one from Denmark and Germany. Results: The HRDQ had good internal consistency (Cronbach’s alpha range.83–.88) and test–retest reliability (intraclass correlation coefficient range.71–.90). Convergent and discriminant validity were supported by high correlations with ReQuest™ and ability to differentiate between groups based on ReQuest™ cut-off values. Responsiveness of HRDQ was demonstrated by moderate to high correlations with ReQuest™ change scores and time with symptoms. An HRDQ cut-off value of 0.70 for definition of ‘bad day’ was also evaluated. Conclusions: Based on existing evidence, the HRDQ is a valid and reliable measure of GORD symptoms that can be used as a study outcome in clinical trials.