BACKGROUND: A previous single-centre study showed that lower oesophageal sphincter electrical stimulation therapy (LES-EST) in gastro-oesophageal reflux disease (GERD) patients improves reflux symptoms and decreases oesophageal acid exposure. AIM: To evaluate safety and efficacy of LES-EST in GERD patients with incomplete response to proton pump inhibitors (PPIs) in a prospective, international, multicentre, open-label study. METHODS: GERD patients, partially responsive to PPIs, received LES-EST. GERD health-related quality of life (GERD-HRQL), daily symptom diaries, quality of life scores, oesophageal acid exposure, and LES resting and residual pressure were measured before and after initiation of LES-EST. Stimulation sessions were optimised based on residual symptoms and oesophageal acid exposure. RESULTS: Forty-four patients were enrolled and 6-month data from 41 patients are available. Hiatal repair was performed in 16 patients. One device-related, one procedure-related and one unrelated severe adverse event were reported. GERD-HRQL improved from 31.0 (IQR 26.2-36.8) off-PPI and 16.5 (IQR 9.0-22.8) on-PPI to 4 (IQR 1-8) at 3-month and 5 (IQR 3-9) at 6-month follow-up (P < 0.0001 vs. on- and off-PPI). Oesophageal acid exposure (pH < 4.0) improved from 10.0% (IQR 7.5-12.9) to 3.8% (IQR 1.9-12.3) at 3 months (P = 0.0027) and 4.4% (IQR 2.2-7.2) at 6 months (P < 0.0001). CONCLUSIONS: These interim results show an acceptable safety record of LES-EST to date, combined with good short-term efficacy in GERD patients who are partially responsive to PPI therapy. A remarkable reduction in regurgitation symptoms, without the risk of intervention-requiring dysphagia may prove to be an advantage compared with other anti-reflux procedures. ClinicalTrials.gov Identifier: NCT01574339.